Flashed to Beta 4.1 (6.5.x) and it's just as smooth and clean as Beta 2. HTC Messaging seems to be pretty OK for some reason, perhaps it's because I have no messages now? Music tab is still useless, playback stops/stutters every few seconds. Will check into previous poster's info about Gracenote, but I had this problem with Sense 2.0 as well
I still have some soft-reset lock up issues, and had a lock-up on my first attempt to flash to 4.1 (locked on tri-color screen), but that's not a big deal to me, if I'm soft-resetting the device, I'm "there" to make sure it boots up properly. Absolutely no lock-ups/issues once it boots successfully, and that's the most important thing.
Overall, I'm still a huge fan of this ROM. HUGE. FAN. It makes my Imagio 100% better, and I'm very very grateful for your effort, Doc.