Pros
-It is well built as already stated. The Pre felt cheap in my hand, like it was a toy cell phone I bought for my Niece.
-Dialer app is smooth and quick. I had so many issues with the Pre's dialer lagging so bad I don't even want to start.
-The phone overall is smooth and quick.
-Tons of nice apps and widgets.
-HTC Sync allows you to sync your Outlook with your phone free of charge. I still cannot believe Palm makes you by a third party app for $29.99 just to do this.
-Facebook Sync will only sync Facebook accounts to the contacts you have in your address book. With the Pre, when you would sync with Facebook you got all of your friends which took up space in your Contacts with people you more than likely have no intentions of ever calling.
-Auto-correct for Spelling in Texts and Emails is a really nice feature.
-There is a video recording feature built in unlike with the Pre.
-Overall camera quality is 100x better then the Pre. With the Pre I always had somewhat grainy looking pictures.
-The ability to do a search on Google with your voice. This is very useful when you are driving and need the phone number to some place. Just hit the "Speak" button say what you are looking for and it finds it.
Cons
-Battery drain issue after sending and receiving texts with the built in Messaging app. Apparently when you use it it locks the Phone services in an "on" state thus draining the battery quite quickly. There is a workaround for this though until a fix is developed. Basically you disable that Messaging app and install one such as HandcentSMS from the Market. HandcentSMS is by far way better then the vanilla Messaging app you get so bug or no bug, I'd still use it.
-It may take a little time to get used to the OS and the UI as it is different from the Pre. I cannot tell you how many times during the first few days I tried to swipe away an app to close it or an email to delete it. Not really a con though.
Had a Pre for a few months also and made the jump to the Hero the day it came out 11/6. I wont waste your time repeating the good posts above me. One thing I DO want to mention is that if you get a Hero, DL "Dolphin browser" for the internet and set it as your default browser. Runs a lot better than the standard HTC browser AND uses "Palm-esque" gestures to execute web commands like "back, forward, bookmark, etc"... It doesnt currently utilize multi-touch, so no pinch and scale. However, there is a zoom tool which is quick and easy to use... a MUST have browser for Android...