Vista Tryout

I am thinking of making the jump to Windows Vista (Ultimate 64) in the very
near future, as I am building myself a new Clovertown computer. From what I
hear, however, at this point in time there are serious driver issues with
many major hardware manufacturers (including nVidia and Creative, to name a
few).

I also heard that it might be possible to try Vista before purchasing a
license. I am, hence, interested in trying out Vista to see if it causes
problems with my specific setup. How do i do that? Will I be able to return
the Vista DVD to the seller for a full refund in case things do not work out
as expected?

Otherwise, is there any way I can download a trial version which I can try
for a limited time before registering? (Note that I reside in Germany.)