Rated 5 out of 5 stars
Looks like the issue with the too-large search icons has been fixed. I just switched over from OmniBar due to a input-related bug.
This one is working great (and sans the bug from OmniBar :) ) !
I'm also running v22 and all of my search icons -- including the larger ones like google and duckduckgo -- look fine and fit within the search bar (I have a few non-default ones as well)
Disclaimer: I do have 1 Stylish style installed ("Firefox 4: Bookmarks Toolbar above tabs, enhanced"), but I don't see anything in there for increasing the size of the address bar... just changing the order things are displayed in.