I replaced the Celestion G12T-85 in my Rivera with a Celestion Century Vintage, and was well pleased with the results.
Tonally, the sound is noticibly brighter, but I like that. Weight-wise, it shaved 4lbs off the weight of my combo, which was a god-send.
Highly recommended from me, but I can see how some people could find them a touch on the bright side. My best advice would be to try one out if you can.
Cheers,
Jordan.