I have a suggestion...two, actually:
1. One of the things that an Enterprise CMS does for you is manage URLs. Sitefinity has awesome URL rewriting capability, but when you use the controls to pick a page, and that page gets renamed or moved, the previous link to the page is lost. MCMS handled this very well by storing the GUID of the page as a link, and then rewriting the URL in the stream to the browser as necessary when the page is rendered. This function was core to the CMS, as I remember a salesperson demonstrating that feature when it was nCompass Resolution, before Microsoft bought it. However you decide to implement it, I think ensuring that no internal link is ever broken would be very nice.
2. There are several related things that could be improved. The <head runat="server"> has a number of side effects that are frustrating, among them the inability to add your own controls to the head section. I've found workarounds for these, but they're kind of hackish. The ability to control stylesheets through the use conditional comments is critical to writing good CSS without resorting to CSS hacks. I've posted on this before (http://www.sitefinity.com/support/forums/support-forum-thread/b1043S-bamckc.aspx), and suspect it's already on your radar, but thought I'd mention again. You should use the same techniques in the <head> section as you do everywhere else, namely using controls to inject theme stylesheets, scripts and other stuff. The SharePoint additionalPageHeadDelegate is a powerful feature as well.
Thanks for listening! ;^)