Scroggs has it absolutely spot on. The only thing I would add is the time to command. I was quoted about 8 years when I joined (post 9/11 but pre-recession) so worked on roughly 10 years. Due to lack of expansion, the increased retirement age of 65 and perhaps most importantly the age demographic of our captains, many of whom are relatively young (mid 40's), it is now very clear that time to command is now more likely to be 15-20 years. This is BA territory but at least they have the option of an earlier short haul command or training positions for long haul SFO's to alleviate at least some of the frustration.
As with everything it comes down to personal preference and an individual's professional ambition. Just be realistic in your expectations and if an early-ish command is important to you don't even think about joining Virgin. If, however, sitting in the RHS for that length of time isn't going to be an issue for you, go for it. I like most of the places we go on the 340 and I like most of the folks I fly with. Just don't expect to see many of the crew downroute and if you want parties and shenanigans, go to Hedonism...
Finally, do be aware that VS is a small, stand-alone airline. RB certainly looks to have had enough and a take over could lead to significantly altered Ts & Cs, particularly the removal of our 750 hour limit, albeit kicking and screaming. That would equate to another trip per month and yet more time away from loved ones. Certainly wouldn't make people's personal lives any easier (although I'm sure it might for some!)