I have the first days of heavy XPages development behind me. I cannot reveal what I'm working on yet (even my collegues don't know it :-) ). But the project contains a lot of elements which were very difficult to do with traditional Domino web development. For example things like:

• Looking good.
• Be userfriendly.
• Using modal dialogs with embedded forms.
• Refreshing only parts of the UI intead of reloading the whole page.
• Displaying data of multiple Notes document in one modal dialog, including RichText.
• Rating system for documents with live-refreshing after you did a rating.
• Multiple views / repeat controls on one pages, with pagers.
• Changing parts of the UI after user clicked a button, without reloading the page.
• Nice field validation on fields.
• Wrapping commonly used code in centrally stored components.

And, my opinion so far?

XPages are good. Really good. I mean, really good. One could say: boy, I cannot find words for how cool they are.

It takes a little time for a traditional domino developer to get used to all the new XPages stuff. But after you got the basics, developing with XPages is so freaking productive and elegant, it's pure joy to work with them.
And: it's something you can give a Non-Domino developer without having him laugh at you.

I developed stuff which would have taken weeks with traditional Domino development in about 15 hours. And that includes much learning work. And everything looks nice and good right out of the box. And I know what I'm talking about regarding traditional Domino web development, believe me.