The Treo 600 is good, not great. It definitely improves upon the Treo 270 but I think the 600's keyboard took a turn for the worse and is much harder to use. The external card is the best feature as far as I am concerned and it does have a much faster processor. I noticed it right away when I started loading programs. The camera is downright awful! I love the 5-way navigation.
If I could improve it, I'd put a normal sized headphone jack on it, bigger keyboard and more internal memory. Not everything works with the card so you have limited onboard memory. Also, the graphics are terrible and I'd make it harder for the card to come out-right now it comes out all of the time. Plus, I'd make it harder to switch between audible & vibrate. I can't tell you the number of times my phone rang after I put it on vibrate.
Overall, I'd grade it a 'B' and there are definitely ways they can improve it. That's why I like to upgrade every year. To learn the latest on the Treo, check out
www.treocentral.com it's a good website with good treo resources. Enjoy!