Here's what I do, I shrink a partition on my HDD (or have it already partitioned so theres space for several OS partitions, Then I install the latest and greatest on the free space or a much older distro partition, leaving my current work distro safe on its own partition, Next I copy over as much of the contents my current home folder as I can. Now, I can truly "taste" the new distro and if it isn't a good transition…
And of course, you can always use KVM's to take a look at distros as well.