+1 ^^
It's not hard to get working, just choose POP3/etc option and then enter your login info.
But you probably don't need 2 parallel mail clients, and I don't see that it's at all superior to the native Gmail app also on the phone. In fact, I couldn't find any way to open a PDF attachment in HTC Mail--I could only read that there was an attachment. Viewing the same message in GMail, I could tap the link and download the PDF, though the app wasn't smart enough to invoke the PDF Viewer directly (is there a way to globally associate file types in Android?)
The one nice thing I found about the HTC widget is that it displays the # of new messages in its home-screen icon...I wish the Gmail app did that. You can leave the widget in place for that reason alone, but unless you use HTC Mail to read your messages, the count becomes inaccurate, I'm finding.