I run several Linux partitions and always run a stable release for every
day and the latest experimental release. I sometimes use VBox, but prefer
to do a full installation to test it fully. I run K/Ubuntu from the first
alpha to final release. At some point I decide that the experimental
release is ready for prime time and upgrade my stable release. I have done
this for many years without a hitch. I find this gives me a better
appreciation for the development process and submitting bug reports helps
me feel a part of that.

In a typical week I boot into each distribution for at least part of a day.
I install each major release for the top distros and a few smaller
favourites. I try to run one of them for several days at a time. I can
access my home from each distribution because I share the same home
partition on each. I have roy, roy-fedora, roy-suse, roy-experimental,
roy-sabayon etc. all on my home partition. A 2 TB HD permits lots of space
to play. :)