You gotta love the learn to search welcome crew, thanks for contributing. I (like Lupin presumably) recall several discussions on the topic but couldn't find them.

Regardless, it is both personal (custom to what you want) and now more than the last few weeks become a time sensitive question.

As Mara said in a few days 2008 non-beta should be out. The only official information is 'some time in december'. I would hope somebody has an unofficial hint as in any day now or December 30th.
{Edit: I take Mara's comment as an unofficial hint}

The only reason to stay with 2007 is if there is an app that you have to have that's not available in 2008. That will remain true even after the official 2008 is released. As a new user with no 'favorite apps', I'd say go ahead with 2008beta, it should be the easiest to transition to 2008 standard unless you can put it down for the next few weeks waiting for the official release (not likely).

For available apps use ITT's Wiki, not the nokia site. They direct you to install a lot of apps like Skype that don't actually work right yet. I doubt that the new OS release will affect how any apps work. I would also assume that apps installed on beta would be able to be restored on the official release. On the contrary 2007 data or apps can't be recovered once you go to 2008.