- The interface, while consistent with the rest of Google, is just so... ugly and engineer-y.
- Practically everybody just uses it as a place to import their Google Reader shared items. It's a more natural fit than Reader itself, which just doesn't feel conductive to the "social" aspect.
- I wish it realized that if I'm following someone in Google Buzz, then I don't want to follow them in Google Reader. Otherwise I'm just getting the same content in two different venues. It only takes a click to "hide" people from showing up in Reader, but still.
- It's nice that it's in Gmail, it gives you something to read after you read your e-mail. I hope they give you the option of having it in Gmail once it gets its own page.
- It makes a ton of sense that changing something in one Google service will be applied across others, but I don't like how changing your name in Buzz/Profiles will also change your name in Gmail.
- People keep talking about THE UPCOMING GOOGLE FACEBOOK-KILLER, but I think Buzz+Profiles+Picasa already makes for a decent-enough social network. There's a ton of room for improvement, though.
- MSN/Windows Live and Yahoo! have also tried to retroactively turn their userbases into social networks, but Google's attempt actually feels like a somewhat natural extension.
- My biggest gripe is that it notifies you when some post you've already read has been commented on by people you don't know. What do I care? It actively discourages you from following popular people and constantly brings up old stuff to the top of your "stream." That makes sense for message boards and e-mail conversations, but nobody in the world eagerly awaits blog comments, which are what these are.
Anyway those are my thoughts, I hope you liked them