By now, which hasn't been long since the initial release, it's a worthy spiritual successor to the gem that was Super Deep Throat. I don't think I have explored everything yet and it is more of a first-impression since I will wait some more.
It's not finished and I'll be greedy: It shouldn't ever be. That is unless there are really no more ideas/positions/options to implement but with currently three positions, a lot of options and only minor chinks, it deserves an 8/10 at least. It's a 9.5 for me since proper a 'Ahegao' expression is a must-have for me and is the primary reason why I will hold off just a little longer.
Distinct options would obviously be nice for all but at least I 'believe' in the base form of Ahegao: Wide open, Not totally white eyes/Half of the iris, simple up and normally sized iris. Others sure can and do prefer half closed, total white eyes (both combined are the case here when blowing hard) or very little iris, cross-eyed and small irises (those do exist other styles).
After that we can talk about other more 'debauched' facial expressions (imho, feel free to talk about whatever you want). There exist more variety than is currently implemented but its acceptable since the two-non-BJs are very new.