Those who have been waiting with upgrading to TextMate 2.0 should do it before upgrading to Yosemite. While 1.x will function many of the older bundle items rely on outdated system components not available in Yosemite.
This also marks the transition from alpha to beta for 2.0. Don't let the beta designation scare you, this simply signifies that there are still planned features left to add. However it is already leaps and bounds above what 1.x offers with many people already using it in their everyday workflow.
As you transition to 2.0 you will find many great new features and improved bundles made much easier to manage with an included bundle manager in preferences. We have several blog posts detailing some of the new features. If you have problems finding a feature you can ask questions on the mailing list or contact us via email or Twitter. While still a work in progress you can also consult the manual, this will be filled out further in the coming months.
2.0 is a free update to all except those who purchased through Mac Heist for which there will be a modest upgrade fee.