I guess I have a soft spot for the v1 of Gallery (website) over the newer fancier v2. I've installed, hosted, configured, and maintained a lot of Gallery installation for friends as favors, and Gallery v1 is simply less of a system hog overall. I still follow v2 development closely but I have my primary gallery on version 1.
You can read about the new version of Gallery here.
Due to the massive CSS and layout changes, it is highly recommended that you backup up your gallery before upgrading. Of course, anytime you do a software upgrade, you should always have a known good backup beforehand.