A lot of people see names like Mesa Boogie and automatically lust after it... not because they're ever played the amp or heard it... just because the name it bears. Being a gear head, I don't give a rats ass whether the amp I'm playing is a Mesa, a Marshall, or some Wal-Mart brand... as long as it gives me the tone that I'm looking for.
Same holds with guitars for me... But I still haven't found a finer guitar than an American Fender Stratocaster...
As for the Mesa amps, I would suggest playing them before making any decisions. Never invest that much money in something you're not 100% positive about. And also check out some amps like like the Peavy 5150 and XXX. They're studio quality amps that get great high gain and don't compromise the clean tone... A lot of Mesa owners that I know have to bite the bullett on the clean tone which is a sacrafice I would NEVER make given the style of music that I play... But if you just play high gain stuff you'd be right in the pocket.
I'd say try them out for yourself though. A lot of people let themselves get ifluenced far too much by reviews and others opinions about the sound of amps. The biggest thing to realize when reading reviews or taking in personal opinions is to focus on what they're saying about the functionality of the amp... What options it has, what options it lacks... how the knobs work, how the functions work... does it have EQ, is it tube or solid... all that type stuff and ignore things that talk about personal opinion on the sound and tone of the amp unless it's something that has to do with volume... Form your own personal opinion of whether or not the amp sounds good. You're the only one that really knows what tone you're looking for... atleast if you're looking for a Mesa you SHOULD know what you're looking for as far as tone goes.
Good Luck man, and remember the only opinion that matters is your own.