Custom ring-back tones are gone - my British friends used to get something that sounded like home.
"Call Presentation" is now settable by group and address book entry - finally, I no longer need to press "1" to accept a call from members of my family. When I pick up the call is immediately connected. This is different form the GrandCentral call screening options. There, I could either screen everybody, screen blocked number, or screen nobody. This finer-grained control is something I (and others, I suspect) have been waiting for. There does seem to be a downside, though. If I have call presentation off (aka connect on answer), there's a chance that my home answering machine, my work voicemail, or my mobile voicemail will answer even if I don't, and then the advantage of Google Voice's voicemail is lost. I'll need to check up to 3 places if I don't pick up fast enough.
Custom greetings seem to still be available.
Voicemail messages now get transcribed to text. By default the transcribed messages is e-mailed to your GMail account. You can still also get notification of new voicemail via SMS to your cell phone, but now the SMS message has the transcribed message (at least if it's short enough). Nicely, the voicemail notification now comes from my Google Voice number, rather than some seemingly random SMS number. That allows me (at least on the iPhone) to call that number and then pick up the message, in case the entire thing didn't get sent in the SMS message or if the transcription looks strange. I've left myself a few simple voicemail messages that were not transcribed all too well.
Text messages are interesting... If somebody sends a SMS message to my Google Voice number, it shows up on my phone as coming from some number in the 406 area code. If I reply to that number, they get my reply. If somebody else sends a SMS message to that number, it is not delivered to the sender of the original message. Clearly there is some sort of mapping such that messages from me to that number get re-routed back to the originator. This mapping appears to last at least 2.5 hours - maybe it's permanent.
In addition, if I get a text message from somebody in my Google address book, their name shows up as a prefix in every message I get from them. If they aren't in my address book, then their originating phone number shows up there instead.
That's it for now. Lunch is over and I really should get back to doing what I get paid for. :-)