The thing I hate about TF 2, is that if you're a spy, EVERYONE shoots at you when you're disguised, its basically useless to go as a spy unless you're cloaked because every person that runs by you, WILL shoot at you, regardless if you're on their team or not.
I haven't seen that happen much. Regardless, the fact that you can practically insta-kill all enemy defenses and support structures, not to mention instantly kill anyone at your whim with a backstab kind of makes up for it.
Oh, I forgot to mention something -- they fucked up 2fort beyond belief. The covered bridge isn't a bad addition (even though the snipers are usually too busy shooting at each other to actually worry about people down below, so it's not a huge thing, really) but they destroyed some of the most carefully balanced parts of that map. For one thing, they managed to make sentries useless for just about every room but the flag room, thanks partly to its reduced range and mostly because they screwed up the ramp room. The fact that they made the elevator shaft into a stairway ensures scouts an INSANELY easy escape route. Seriously -- that was one of the things that made playing a class a rocket launcher worth it. Sure, scouts could conc grenade themselves up and out in classic TF, but the wavering view coupled with their high rate of speed made it harder to flee.
Finally, one of the most fatal flaws in 2fort 2.0 is the flag return path. Before you'd have to take the enemy flag to the center of the sniper deck to cap it. If the enemy team was particularly good and missed the flag carrier the first time around, the sniper could cap the carrier and hold the deck. Usually, at that point, people would conc/rocket jump on the deck and defend the flag -- two meters from the capture point. That led to some of the most fierce, intense battles on the map.
Enter TF2. In an attempt to make snipers even less useful than they were in the original, they moved the capture point deep inside of the base. WHY? That further ensures that scouts are practically invincible classes. Thanks to the covered bridge, snipers on the deck get almost no opportunities to cap carriers, even for the slower classes (but especially the scouts -- the only time you could really kill them is with a perfect shot as they're entering the base unless you hop down to ground level, which has its own set of serious disadvantages). If a scout is carrying, it's literally impossible to kill them when they get in the base unless you have half of your team in the enemy base already. I can't think of any other way to describe that design change other than "fucking idiotic." I used to play 2fort4 and 2fort5 a ton -- it seemed like for every QWTF server in existence there were two of them playing 2fort5 24/7 -- but I can't tolerate even playing a round in the new version.
I never was able to get into TF2. It's pretty cool, in my opinion, it's just that I don't have the patience to learn all the little tricks, all the while getting obliterated repeatedly by every other player on the server.
It's really not very well balanced. As for most classes, there aren't really any other tricks besides brute-force. For instance, when you play as a Heavy, ask a Medic to stick by you and keep his charge beam on you. When his Ubercharge fills up, you're invincible. Even after it runs out, the boosted amount of health that Heavies get from Medics (I think it goes clear up to 450) would make it hard for anything but another Heavy to take you down. Likewise, when you play as a Medic, stick near a Heavy and keep your beam on him.
When you play as a Scout, just keep running and jumping. Nobody will be able to come close to catching you, and your double-jump would ensure that you could clear many more obstacles than any other class. In attack/defend matches, pairing up with another scout and capping points together is enough to win your team the game without anyone even breaking a sweat. Odds are, fallen enemies won't even be able to respawn in time to protect any of their points (since it takes longer to respawn than it does for your average 90-year-old to get off without popping Viagra).
If you use one of those three classes and do what I said, you'll probably stay alive longer and score more points. Since the medic's charge beam is ranged, you don't have to worry about "unfair" gameplay elements like splash damage affecting you while you pump up the over-powered Heavies. Trust me. I was dying repeatedly and after I started acting like a complete whore the game became easy to the point of stupidity. The only times I died were when I made the mistake of playing "exotic" classes like the Demoman, Sniper, or...uh, anything that isn't a Scout, Heavy, or Medic.