I have installed it and it was pretty simple.
The real things you need to know :
All your e2 synth project will be basically not useable with the new firmware, because this new firmware won’t have access to the e2 synth sound anymore. You need to see it as a completely blank machine after doing FW upgrade. it’s not a e2 synth anymore, but more a e2 sampler. So backup all your SD card and project before taking the jump
You have access to a really wider “e2 synth” than before. Basically, you keep all the basic waveform, but have access to patch with a +2 +5 semitone, which is definitely a good thing. Some of the patch have FM, which is fun. And yes you can sample and use it as a e2 sampler basically, but with much more power.
If you feed it with the right sample, it is a good thing, because after few years, the e2 synth sample are… Not my taste anymore.
If you want to go back to your old project… That’s a definitive no.
I really thanks this developper to have done that, it make this e2 came back to life for me
Last, if you want the FW I can give it to you.
Don’t know if there is private message here, but I should be able to give it to you if you share your email in a way you won’t be spammed.