I'm going to find this a hard review to complete not because of a fault of the product but because owning one nearly turned me off completely from electric guitar.
First off, I was desperate to buy a Kemper for my studio as it represented the most satisfactory way of recording guitars without resorting to isolation cabs. When it first arrived, I profiled my amplifiers before selling all but one. The profiles were easy to do and very accurately represented my amps. The quality of the Kemper was beyond reproach but once setup in the studio I found I was playing less and less and when I was playing I was auditioning profiles and settings more than enjoying playing guitar. During this time I completely lost interest in the guitar and got more enjoyment out of keys.
A couple of months ago, whilst trying to scrape together the money for acoustic treatment, I decided to sell the Kemper. It has taken a couple of months to get back to enjoying playing again, now with an amp. What seems ironic is that the amp I play through was the same profile I used 9 times out of 10 on the Kemper and the profile accurately reflected the sound of the amp. The only conclusion I can draw is that, for me at least, whilst the Kemper sounds great and is very well made, it isn't as enjoyable and as inspirational as playing through a proper amplifier. For a composing studio musician that is a serious drawback.