For what it is worth, I just got my Hero on Thursday and I love it. I've been on Qwest wireless in Minnesota for years with a very old phone. They are ending their wireless service Oct 31st and forcing everyone to move to Verizon (for whom they are now a reseller/partner), or jump ship to another carrier. I stalled as long as I could to see if Verizon would come out with a phone I liked, since their coverage and service is excellent locally. But they didn't, and when the HTC Hero was released by Sprint on Oct 11th, I ordered one. Thought about the iPhone but I hate AT&T and also don't really like the "our way or the highway" mentality of Apple, much prefer an open platform. Also AT&T seems to be struggling to handle the network traffic and has a lousy service rating locally. I depend on my phone for business use (work from home), so network reliability is critical to me.
From my experience so far, it is not laggy at all, not instantaneous but very acceptable speed when launching apps and running them. There is an "app killer" app that you can download that shows which apps are running and lets you end them. Avoid CPU hogging programs (twitter is one).
The screen shuts off in 30 seconds by default, but there is a setting for that and you can even set it to stay on all the time if you don't care about battery life. The UI works fine and is quite intuitive, I got used to it fast. The keyboard is pretty good considering the small space (works better in landscape mode), and the word completion/correction is excellent. The camera is high res and easy to use, with auto-focus. No flash though. This phone comes with a lot of features, WiFi, Bluetooth, GPS, SprintTV, email, web browser, and thousands of free apps on the Android marketplace.
For more evaluations and critiques, look up "HTC Hero" in YouTube, there are a number of good videos that show it off. The CNet one is good, also MobilityToday.