I am wondering if there will definitely be a Windows Version of Ubuntu One after the beta? Because otherwise I will not bother getting a 20gb plan as I dont use Ubuntu on any pc.
Yes, there will be a windows client after the beta. Currently we have the beta to test the interaction with the desktop and the possible problems that we will have.
Regarding the interaction with the desktop, we are also porting desktopcouch to work n windows which should bring your contacts to that platform. Tomboy sync already works on windows and there are plans to help banshee to be ported to windows so that we can offer th music store there.