I really like MIUI. Super smooth, and INSANELY customizable. It's really impressive. I think a great deal of the problems reported are because (as with most problems with any rom) most don't do a full wipe.
I ran 1.8.5 with tiamat 3.3.7 for stretch and really loved it -- I did need to flash gapps w/ vvm
from their guide (market is already there, but I need my vvm and other google apps) and the
gps fix on xda. I then tried to update to the next build using the native MIUI backup app, and had all kinds of issues -- but then did a clean install and only used the native backup app for restoring my screen setup/folders (and tb for apps), and it was great.
I haven't tried
1.8.26 yet (been busy trying many other roms), but am itching to do so. The only reported complaint I've seen that worries me is those reporting slow 3G speeds with this build, so those of you running it I'd love to hear your experience with that...