^ Adding a couple more:
•the ability to grab, hang on and climb up on ledges.
•to shoot as a bird

Also, has anyone got into the birdland located in the lab world? The level is there (Labrat 3) But I can seem to find the seceret warp there.

I noticed what they say about 3d realms and ID software is that they work on a game until it's perfect, then worry about release dates, instead of rushing the job to meet christmas shoppers, for example (atari tried to do that with a ET game in the late 80's, but it was so rushed, no creativity was added, and no one would buy it. And they Mass-produced the suckers!)