Well, lately it's been 2100-2200 max, with 1000 or so minimum. Pre-1.52, it was usually 1600 peak. Apparently they released the game in Australia this week or something, and the 1.52 infantry predictor improvements have made infantry somewhat more enjoyable than stabbing yourself in the eye with a fork. Infantry sort of works now.
There's game-imposed limits on certain vehicles to keep some sense of balance. The "better" equipment is in rare supply; you need to take a mission to have a better chance of getting it, or earn rank. But that still doesn't guarantee you one. It's really not that bad a system; just means you won't always be able to get a hot ride from a close base. And yes, sometimes you may not get a hot ride at all, but there's always a vehicle of type. For planes, that means the Hawk 75 or the Hurri on Allies, and the 110 on Axis.
With 1.52, there seems to be a LOT more infantry. Before, it was maybe 2:1 armor:infantry ratio on attack. Now it's a lot more common to see the ration reversed. On defense, infantry is a lot more prevalent. Certainly makes the battles more interesting.
As far as air, there's usually a few planes flying around each hotspot. Bombers are pretty important in the game, and vulching a truck can ruin a nicely planned offense. With the fields separated so much, there's hardly EVER any vulching from planes, but if the field is near a front, you can expect a tank vulching planes, which is annoying. This often means flying a decent distance to find a hot spot, which isn't too bad.
As far as the arena atmosphere ... well, it's ... different. A lot more people = a lot more a'holes. There's also some good people in there if you tune out the morons.
Oh, you can keep track of the server numbers here:
http://www.haukmoor.org/~jasonb/ww2ol/capacity/Pretty interesting stats.
