I caved in and bought it last night. Played single player for a couple of hours and multiplayer for about 3. The single player so far has been expected, top notch. All though multiplayer was not as fun as MW1, it's not nearly as bad as I thought it was going to be. Lag is minimal, the guns and perks are fun to play with, and the maps are balanced (no spawning into death anymore, no position is "safe" anymore).
It does however fall short of the player capacity. I know they say the maps are balanced for 9 vs. 9, but most of my night was with 6 vs. 6. That maybe just because they're trying to get rid of a few kinks in IWNET, but most of the time you will be just running around on the map looking for some one to kill. If you have adopted a run & gun hip fire style in MW1 like I did, be prepared to force yourself to adapt to a different style. Some might see that as a positive, but to me anything that promotes camping becomes quite boring. It does seem the finished product is more of an arcade game.