Yes, crits now have a lower base chance to occur, but the more damage you cause in a period of time increase your chances from like 2% up to 5 or 6. So, you don't just get crits, you earn them with performance.
And I don't see how you can compare a soldier and spies crit kills. Crit rockets are entirely luck, you can't control when they happen, you can only hope they happen when you're firing at a large group. Crit backstabs, however, are entirely skill (minor bugs aside) in maneuvering and positioning yourself behind an enemy. You know what you're doing and that you will (or should, in some buggy cases) get a crit.
It's like saying a sniper is over reliant on crits for kills...they're reliant on headshots, which are skill based, which are just classified as "crits" in this game. Same for the backstab.
I see no problems with the crit system...at times annoying, at times it saves your butt. It just adds, along with the new achievements and unlockables, a hint of that RPG addictiveness to the FPS world. I like it.
And, as far as the original post goes:
Pros: Playing with fun people, knowing that there is a class or classes tailored exactly to what kind of play style you feel like at any given time. The game forces teamwork for success.
Cons: Minor imbalances due to updates being rolled out class by class. Some are left underpowered only because they haven't gotten their update yet, which makes it feel like you're playing an unfinished game at times. Also, when you're up against a good opposing team and your team isn't totally committed to working together to achieve victory, then you may as well just be running around in circles doing the spy crab dance.