Halo's control is easier, but frankly, I can't see the vehicles being ripped directly from Halo, nor the physics, because physics is physics is physics. In the end, so long as you don't fuck up, you're always going to end up with physics that's essentially similar, because it's always going to be based on the same laws. Halo's vehicle feel is of much more powerful vehicles with less grip and fairly bouncy suspension. There's nothing especially terrible about the control, but it can get annoying to be looking one way to shoot and to get stuck on something you can't see.
It took me a bit of time (a few games) to get into Onslaught, but I'm sold on it as a gametype now, and there's a lot of room for mods to play around with it in interesting ways. I'm not entirely sure about the feel of Assault, but it also feels like there's something generallly wrong about the scale of stuff, so maybe I need to play with the FOV a bit.
I can't say I've even looked at CTF / DM / BR / TDM yet, but they were an enjoyable staple before, while the real problem was that UT2003 didn't pack any of the gametypes that would bring me back to it.
I'm getting a little miffed with the server browser always wanting to completely refresh the whole list when you fail to join a server, and that the user numbers don't take into account any spaces that are admin-reserved. It's annoying to have to go through the process each time for a server that says 19/20 yet doesn't really have a slot free. They're also going to need to sharpen up their master servers.
Still, overall I'm positive about it.