I don't post through Google, but have used it extensively to refind my
posts for repeat questions/ers. (instead of having to save and try to find
information on my hard drive).
Viewing it from the POV of someone who posts from Google or searches the
archives, I find it annoying.
I don't need the name hi-lighted in colour. Plain text was just fine.
They don't show the date if the date is current (this year) but do if it's
an older post (previous year). So someone just replied to a 1995 post (on
another newsgroup). The original poster is, no doubt, long-gone.
It's faster and archives faster (almost immediate) instead of 2-3 hours.
That's a plus.
They don't show the posting email address. To prevent spambots from
picking them up. That's a plus.
It's a minus if you're trying to connect with someone who posted earlier.
Or want to refind your posts and can't rememvber what email address you
were using at the time.

The default view used to be threaded. Now it's not. (extra click required)

The default was showing the whole post. Now they sometimes only show the
replier's text. Extra click to see the full post.

Right now, Google posts are duplicating and triplicating. (an old bug,
that's reappeared)

There's a new way to report abuse, (extra click - Show Options) takes one
into a screen where the message ID is.
Good for spam I suppose.
Otherwise their Terms of Service don't have much teeth..

Faster with bells and whistles.

There's a place to report bugs/suggestions
http://groups-beta.google.com/support/bin/request.py

Thumbs down, so far.
J