Whenever a new version of minecraft is released by mojang, keep in mind that it will usually take days or more likely weeks before their are stable mod-able server builds. If you upgrade you should be aware that their will be few if any good servers available to play on right away.
If you want to be able to test new upgrades, but also be able to play on unupdated servers I recommend MultiMC.
http://www.minecraftforum.net/topic/1000645-multimc-43-windows-linux-mac/http://forkk.net/MultiMC4.htmlIt allows you to easily maintain multiple independent minecraft installs, to easily upgrade or downgrade your versions, to easily install mods, and to upgrade java graphics libraries easily.
