Opera 7.something on up to 8.0 Beta 2 worked extremely well with GMail. In fact, I had no problem with it what so ever. However, Google decided it needed to make some changes to GMail to support “other browsers”. This was done by creating a basic “HTML view” as they called it.
Well, even though Opera 8.0 Beta 2 worked [just fine] with GMail, they decided to force users to the basic HTML view. Personally I consider that an insult, but anyway…
Hope is not lost, if you want to use GMail and Opera (or any other browser) in the normal view, you can simply go to the URL below.
Note that you may have to sign in first, and then goto that URL in the same window.