Yes. I found the same. The vocals were weak. I believe that is why they added that vocal enhancement feature..it sounded unnatural me tho, like it messed up the eq when used. . You can turn off mid range compensation with the 20 dollar app. You can also correct the range which Audyssey adjusts by using the curtains only up to the first reflection around about 300hz and under. You can also use the sound curve feature to add some boost around where you cross the speakers over. This all helps the sound quite a bit. I never found a way to adjust the 3800 to my musical.likikg despite using the same Audyssey settings. It sounds like you have some work to try with the 3800 yet. I also turn everything off like dymaic eq.
It seems that a lot of people like the way the 3800 "sound", so I have to ask, how sure are you that your perceived sound quality issue is in fact due to the 3800 and not other things? I asked, because while measurements Amir provided do not cover everything that could conceivably contribute to your perceived issues, the extensive tests really did not show anything that could contribute to the vocal weakness that you and surely some other users perceived, and again many didn't perceive the same.
In my experience, vocals in movies have never been great regardless of any of the AVRs/AVPs I have used in the last 10 or more years, but it does seem that it is getting worse with the advanced formats from the plain 5.1, 7.1 to 5.1.4, 7.1.4, 9.1.6, and from DDTHD to Atmos, DTS:X etc. I believe the biggest factor is the recording/mastering itself, just like for music, recoding/mastering quality trumps the quality of mid to flagship level AVRs/AVPs/speaker. In order of importance, in my opinion, people often get their pripority misplaced, they should be focus more on recording/mastering quality, followed by room acoustics, speakers, and then the electronic stuff. Obviously that assumes people already have very decent speakers and are shopping for mid range and higher AVRs, AVPs, preamp/dacs, and power amps. I consider the X3800H the starting point of "midrange" AVR, ommv.