Yeah, and Demomen are significantly nerfed. I don't mind so much that your grenades don't explode on contact with people after one bounce, but it's made killing sentry guns much more difficult, when it was already hard enough.
To be honest, though, I don't mind the change that much. You can't expect the formula to be 100% perfect when the game launches, and any change they make is going to affect some class in a negative way. You can't look at it as "they've made the Demoman useless", you have to look at it like "OK, now I have to play the Demoman a bit differently, and be more careful about taking out the sentries." There are several tools in your arsenal no matter what class you're playing as, and if you still aren't having any success, there are eight other classes for you to play!
I find that when I get frustrated by something in TF2, I start thinking, what else could I try to get past this obstacle? Instead of bouncing grenades around the corner, maybe I should edge up to it so I'm just out of the gun's line of sight, and toss 4 or 5 stickies next to it and detonate. Perhaps that will work, or perhaps someone will see what I'm doing and come kill me before I can destroy the gun. Maybe I should try a more direct approach with the Soldier. Maybe I should try a more sneaky approach with the Spy.
Then, when the round ends and I'm on defense, I'll be an Engineer and put a sentry gun in the same place, and see what people on the other team do to try and destroy it. It's easy to get fed up with TF2 if you're on a losing team and just can't seem to do anything right, but if you just take a step back and think about what's happening, you can often turn a bad situation around even when it seems impossible. And even if you fail, you might learn something in the process that will help you next time around.
I really like the time period immediately after the first release of a game like TF2. Essentially, everyone is a n00b! People may have varying levels of skill, but no one knows any of the new maps, no one knows the best places to put a sentry, or the best ways to organize an offense to break through a given location. There are so many combinations of things to try, that every game you play is different, which keeps it highly interesting.