This VST was a nobrainer for me as I was searching for a orchestral library and it ran on a great sale. The sound quality varies from amazing to mediocre. Overall, strings sound extremely well, with a bit of attention to detail one can really make it sound like a real string orchestra. A LOT of different artifulations along with the divisi sections make it a very powerful tool. However, it's uncommon for a string library to sound bad as it's always the best library of the whole orchestral series of every vendor.
Brass and Woodwinds really depend on the instrument. Some sound great, some really don't. Everything can be blended together and than sound great, however some solo instruments (mainly WW) simply can't be used solo. There is also a problem with instruments losing a volume rapidly with the lower pitch. I know it's natural a french horn is loudest in the middle to middle-high range and rather lyrical and sofr on the very high end and low end, however you almost can't hear a6 horns on the few lowest notes.
Both pecrussion and harp sound really great, though some harp patches are extreme velocity sensitive (and I say that as a pino player for 20 years). Solo cello and violin are absolutely horrible if you have like NI Cremona Quartet or Spitfire Solo Strings. I uninstalled those right after I tried them for a while. I guess for supporting a melody in a mockup they could do fine but after hearing them alone I simply couldn't use them anymore.
The biggest deal is everything connected to the download / installation process. I have really fast internet connection, with a fast ethernet cable I can make platforms like Steam, Ubisoft, Native Access, Sine and dozens of others to download 30-150MB/s depending on the platform and other variables. However, EW Installation Center doesn't download faster than 3,6MB/s. I didn't go for the box version because they state they use extremely fast Amazon servers but the download process is simply horrible. If I could give an advice to anyone, as the sound quality really is there, if the only option you have is to get the download version, pass it. Their servers are the worst I have ever seen. What I could possibly download within a single morning takes almost a week of constant day / night downloading.
Also quite a lot of libraries download incorrectly. During my first install, most of the tuba articulations didn't download and install correctly, ending up with just a sustain articulation working. Also generally at least one articulation in EVERY (!!!) brass and ww instrument patch wasn't working. Et voila, redownload everything and install it again, hope it will work well.
The Opus engine is also the only one that requires special treatment in a daw. For example, I never changed the input channel of any instrument from the default "omni". With EW, I have to change every single instrument input to Komplete A61 -> channel 1. Seems quick and easy but it's really annoying when working with the full orchestra. If you don't do that and leave it omni, the instrument will recieve every note in every other instrument as an input. Also there are other details that must be done with this engine only in a daw but there is no point to elaborate that.
My overall rating is:
Musical Sound Quality: 9/10
Technical and other parameters: 2/10