Well I have built 3 of them so far, but I guess I'm not the reference you're looking for
I know about at least 2 other guys who have built one according to my construction manual, and both have let me know that the device works great on their Emulator-II.
The second E-II owner initially had trouble with his Rev1 EII, not with his Rev0 with retrofit RS422.
But we looked for a solution together for that Rev1 and were able to solve it by adding 2 capacitors. I tested it on the two Revisions myself too and it's fine now. The latest version of the construction manual contains this fix already, so it's up to date.
From Emax side I have not received a lot of feedback... but I guess it works well on the Emax-I.
On Emax-II I *know* there are some problems with sample transfers (not bank transfers) with some revision numbers of Emax-II, but the problem is also present when using Alchemy or Sound Designer. So... I consider this a bug in the RS422 implementation of the Emax-II, not the EMuSer...
Anyway, I'm also very interested myself in feedback from people who have built the EMuSer.
So for sure I will follow this thread too !
///E-Synthesist