I switched from the Moment to the Hero just a few days ago. I had the Moment for close to 45 days and became very familliar with it. I could not be happier with the switch, and believe you will be as well.
Even though the processor is supposedly faster on the Moment, my Hero is SO MUCH more responsive than my Moment was. I believe this may be in large part to the Fresh ROM 1.1 I installed, even though out of the box the Hero was very snappy to begin with.
There are so many "quirks" and bugs with the Moment, including the GPS issues (total bummer), the battery meter, proximity sensor, sluggish notifications, incompatible apps (Pandora, anyone?) etc.
Everything works the way it's supposed to on the Hero. Other pluses include the Google Voice Search (an Android standard, missing from the Moment), the LED notification, multi-touch, the much better trackball, and the sleek, sexy, pocketability. I don't miss the hard keyboard at all - the Hero's on-screen is almost on par with the iPhone.
Don't be fooled by Moment fans and other vanilla-Android users. Sense-UI makes Android SO MUCH BETTER. If you've only used one or the other, there's no way to really appreciate the improvements. I still can't beleive how much easier to use it is.
Having been through so many phones in the past 2 years (Voyager, Dare, iPhone, Moment, now Hero) - I can honestly say I can see myself with this phone for a long time. Will all the exciting new Android stuff out (Droid, Nexus, etc) it may be easy to be tempted to wait for something bigger and better - but this phone is absolutely wonderful.
Hope I made your decision a bit easier