Thanks A,
1. I think the OG questions were much more realistic, as were the GMATprep practice tests. The test prep companies have material which may actually be more difficult, but isn't quite in line with what you'll see on the test.
2. The GMATprep was the best indicator for me. The CATs of the test prep companies are difficult, and hence good to train and stretch your abilities, but take the scores with a grain of salt. The best analogy I can think of is running "broken 4's" in track. Whereas a 400 meter sprint is one complete, all-out lap around the track--already a grueling challenge on its own--broken 4's require you to sprint 300 meters, break for 10 seconds, then sprint the final 100 meters (a "broken" 400 meters). After 10 seconds the lactic acid has flooded your exhausted muscles, and the final stretch is agonizing- much worse than the real race. Test prep CATs are your broken 4's. Push yourself knowing that you will do better on the real thing.
3. I did freeze up a bit on some practice tests, ironically (to me) on the AWA section. This may sound simplistic, but my best advice is "just do something" (keep it simple, take a quick best shot and move on--you'll get the next one).
4. Easy- no. =)
Hope that helps; feel free to ask more questions if you'd like to.
Good luck!
Matt