Hi,
It may depends on what type of projects you are creating. I have experienced it working, but then I have only done it with 1 solution which contained a WPF and a Class library.
I wanted to do something similar, see here in my project on codeplex
Like I said not sure if this will work for you, but it did for me.
I was working on this at home and at work (not work related just for fun) I had a copy of 2010 beta at home and 2008 at work.
I initially started at work using vs2008, so when I went to open my project it brought up the upgrade wizard.
When I got to work the next day I chanced my arm and created a blank solution included the existing projects into this and saved the solution out (calling it something slightly different)
So when I was at work I was able to run the vs2008 solution file make some changed update those to codeplex and the when at home I could get the latest changes and open them using the 2010 solution file.