Hmm, let's see... changes to char gen, task system, skills tweaked, recoil, combat system, updated the equiptment to include known and expected vehicles and goodies...
That's off the top of my head. I have both. I either use 1.0 or 2.2. I never use 2.0 for anything but as a paperwieght.
Of course YMMV, but I'd suggest trying to find a copy of either of the others as 2.0 is a mess. Go to http://www.geocities.com/cavscout031/comparison.html
for an excellent summary of all versions of the game.
T2K 1.0 was a box. 2.0 I got as a book. I've never seen any 'refs screen'. From the summary, I get the impression this might have been what was in the refs screen. But what format was 2.2? Electronic download? Rare dead tree format never yet seen by me? Was it published as a book by GDW?
Inquiring minds (or no-minds, depending on the day) want to know!
The ref screen came with a pre-release of the d20 rules and a short module if I recall. V2.2 was a book release as well. Looked just like 2.0 but had a star on it with 2.2 in it.
GDW attempted in its last days to make all their gamesystems playable under the same engine. It was a good idea but didn't take at the time. Because of a bad decision to support Gygax's last work, the company went under. Very sad.
V2.2 is a hard book to find. I have only seen one on ebay, though I haven't looked for awhile now.
The mix of folks I have visited with are split between v1 and v2.2 as their choice of play. I liked 2.2 myself.