Fender Mustang GTX100

I've been using valve amps and an array of pedals for years for live gigs and practice. They sound great but they weigh a ton. I decided to look for something more portable with built in effects that I can just turn up to gigs, plug in and play. After trawling through the internet I narrowed it down to the Boss Katana and the new Fender Mustang GTX. After comparing the features, price and the fact the Mustang GTX100 comes with a footswitch, I opted for the Fender.
I've now been using the amp for a while now and am very impressed.
The presets are great with sounds for most types of music. It has a load of amp models, cab models and effects which you can use to create your own patches or alter the presets. Each parameter is tweakable from the amp or from an app you can download on to your phone and links to the amp via Bluetooth.
I'm not the most technically minded man in the world but I managed to work out the app controls in about 10 minutes however, if apps aren't your thing, it’s not essential. You can, however, use the app to create playlists so that you can keep the patches you use most often together in one place. This would be very useful in a gig situation where you could have a different patch for every song if you liked.
You can add up to five effects to each patch but be aware that some patches seem to take two places rather than one. I guess this is to do with how complex they are. The effects are very good with something for most situations. There are a few that are only really useable if you buy the expression pedal (wah and pitch shifters). You can alter the order of the effects putting them before or after the preamp (as you would with an effects loop).
There is a very useable looper giving you 60 seconds of loop time. I’ve never been that keen on them before but I’m very impressed with the sound quality on this one.
If I had to find a downside with this amp I suppose you could say that there is perhaps a bit too much you can tweak. Once you start twiddling and meddling it’s hard to stop.
I suppose the main question to ask with any modelling amp is does it sound as good as the amps it’s trying to emulate? The answer is obviously no, but it’s very close. I was expecting something that sounded synthetic but it seems to react well to playing dynamics as a valve amp would. The Fender amps sound especially good.
It's easy to use, lightweight, loud and sounds good with a huge array of options on tap.
A very good amp

I love this Amp. It is a very complete offering with a great sound from the Celestion speaker. The amp comes with connectivity by wifi, bluetooth and Fender Tone App. The Footswitch is really essential if you want to bring out all of the features. If you are buying any of the GTX amps, I'd recommend going the extra money for the footswitch if it is not included in the price.
I find that the presets I created myself or those user presets I have downloaded from the App are much more useful than than the 199 presets that are preloaded by Fender.
I like being able to group my favourites side by side on the footswitch. I have 1 minor gripe about the GTX 100. The Bluetooth feature has a delay and when you are watching a Youtube video of a guitarist playing.
Their fingers will be at least 1 second out of sync with what is playing through the amp. There doesn't seem to be a fix available for this yet. On the PRO side, the Amp is very light and very loud! You could gig this Amp no problem.
I use it at home. I have never gone beyond the 1-1.5 region on the master volume - it is just SO LOUD. It is a neat looking amp too. It isn't "classic" Fender in looks but it is nonetheless, visually appealing.

I bought this amp to have the following set of features in one box:
- Effects chain (you can arrange effects in any order, have 3 distortions in a row or 3 delays in a row);
- Looper;
- Footswitch;
- Send / Return / Line out / USB interfaces.
All of the above is perfectly delivered. The amp does its thing well. It sounds good, in 180 presets it has you can find 30-40 tones that sound sweet for you :)
I believe it will be even better with the EXP-1 expression pedal. According to docs, they should be compatible, I'll find it out soon.

Things to consider:
There are some limitations on the number of effects in a chain. For example, you can have only one pitch shifter. Some other effects put limitation on what you can use with them, probably, due to computing capacity of the device.
This amp is LOUD. At home, I set Master volume to approximately 1 - 1.5 in a 0-10 scale. With louder settings, you will be hated by your family members very soon.

Now the problems:
As this amp is so smart and has so many features, it's actually difficult to control them. You can configure the effects chain from the front panel, but you need to browse through every setting with soft keys and a single knob. Quite frustrating.
It's a bit easier with the Tone app that connects to your amp via Bluetooth. It gives you a better visual overview of your effects chain and lets you configure one effect at a time (open a pedal, turn some knobs, move to the next pedal).
What I can't stand about this app is that it immediately demands that you register at Fender. Then, it wants your location data. It's impossible to connect to your amp if you don't grant it access to your location. Why, Fender, why do you want to know where I am???

Summary:
For the price, I haven't found anything with a similar feature set. It's like having a pile of stompboxes, but in one shell, and for the price of two of them.
However, if I had infinite money, I'd choose something that would be easier to configure, and stay away from Fender developed Android apps.

This is the best modelling amp I've ever used. Simple to operate and modify on the amp without even having to bother with the app. But the app adds ease if you like using it that way.

Clean presets are great, with no-noise compression to give a little punch if you like. All the gain presets sound full and true to life, with their different characters depending on the amp they model. And I really appreciate the FX button that bypasses all effects in one press.

The footswitch that comes with this model as standard makes the 100 more appealing as it's only a bit more expensive than the 50 plus adding the footswitch on yourself. It has more than enough volume for gigs and sounds just as good at bedroom levels.

Very happy with this one.

After using it for some time, I decided to expand the review.
This is my fourth modelling amp (before that: Roland Cube, Mustang I and Blackstar ID:Core BEAM). While these before were 20W ones, there is one feature that makes GTX-series my favourite:

You can model the amp through the controls on the box alone. Add stompboxes, adjust knobs, save presets. All of it. Sure, there is an Android and iPhone app that makes it simple and graphical, but if you need to - you can change it with your fingers alone!

My Mustang I had an app (until Microsoft deprecated Silverlight), my Blackstar had an app (until Adobe deprecated Flash). Now, I am limited to the very basic settings on them (unless I am willing to do computer archeology).

What makes GTX (and GT) series different is that even if Apple/Google/Fender moves on, and leave the Tone App to wither, you will still have a fully functional modelling amp. And that is priceless.