Personally I prefer the look and feel of 2010 over 2007. Here are some of the changes that are in 2010 compared to 2007.

http://www.notebookreview.com/defaul...n+Outlook+2010

I don't think there should be any issues with using the pst file with 2007 and 2010. The pst file just holds all of your info like emails,addresses,notes etc.