Well I just got this feat for my monk. I played with it for the first time last night and loved it. What fun.
A few of the nifty tactics I used last night:
1) I would toss an opponent to the ground behind me, landing him in front of my rogue friend who was two squares behind me. Since the opponent was now laying on the ground between us, the rogue was then able to take his held action, getting a full attack with sneak attacks at an additional +6 to hit (flank and prone opponent).
2) At one point I was standing next to a pit when a ghast charged me. I was able to toss him down into the pit.
3) I'm really looking forward to seeing how this works in conjunction with my karmic stance feat as well. If you hit me, I throw you to the ground in front of the rest of my friends and let them have at you. I can't wait.
I really like this feat. It isn't as great as some feats, but it has a few nice advantages. Basically it's Improved Improved Trip. You now get to deal your damage when you knock them down, instead of having to roll a second attack on a follow up to the normal Improved Trip. And it lets you use a touch attack to deal damage (assuming you trip successfully, of course). One of the neatest things is that it lets you maneuver the enemy around somewhat.
It helps to get your trip rolls up as high as you can though. I happen to have a pretty pumped up Strength (21). I also just had a pair of bracers of striking (from MoF) made with +2 sweeping built into them. So not only am I now a +2 weapon, but I get the +4 to trip attacks from the sweeping ability. Really sweet, but very expensive (37,310 gp). I think it was worth it though.
Anyway, I am quite happy with this feat so far.
As to the AoO thing: I don't think it should work like a bull rush. If it did, I think it would say so. The DotF feat shield bash does. This one does not. That would make it much more powerful anyway, IMO. Just be happy tossing those bad guys around and letting your friends get the +4 for prone opponents. That's good enough.