Spoiler

I don't know because I always took him with me in the final fight. His Incinerate is, at least as far as I can tell, probably the best NPC power for eating away Humano-Reaper's armor. If you *do* take him with you in the final fight, he lives (though you'll definitely get a scare!

Qwinn

The editor also has Kasumi available to be edited in, though I haven't tried adding her yet

Seen this on the bioware forums and youtube I think... If you try adding her into the game it causes errors, and might make your game crash. However, it is possible to have her in your party during the suicide mission. Her outfit and face appear to be nothing more than place holders, but the dialouge is there.

As for the Tali/Legion early recruitment, I saw some speculation on that being changed for the console. Kind of annoying, as I wouldn't have minded having to switch CDs more regularly (Yes, I'm a console player) but I actually like the structure of the game so it doesn't really bother me *shrug*

Some of the hidden dialouge is pretty good though, and I'm sure you cna find it all on youtube.