Some (seemingly simple) issues that haven't been fixed:
(a) In the web version, there seems to be no way to curate your "friend list." Despite choosing "Never show," people I've once interacted with via a Craigslist ad keep showing up. Deleting contacts is a pain.
(b) iPhone client lets you enable images in messages. Great! Unfortunately, they don't show up on the web client.
(c) On the iPhone client, past conversations keep popping up even after I "archive" them. They disappear for a bit, and then appear again a few days later.
(d) The GV app doesn't let you make calls inside the app (it insists on calling another number of yours). The GV webpage doesn't either. And yet, the Gmail interface lets you place calls and I use this all the time. So confusing.