So you want the YouTube from Gingerbread, but you want it jammed into your Eclair? You've got strange tasty treat tastes, don't you? Lucky for you, XDA forum member rolle3k has done just what you need to port that futuristic app into your still-yummy Android OS 2.0/2.1 Eclair.
Before you do anything, you've got to remove the default YouTube app from your device. After you do that, get to hacking. All you've got to do is, using ADB, do the following in order: adb remount, adb shell rm system/app/YouTube.apk, adb uninstall com.google.android.youtube. Simple, yes? Go ahead and download all the files you'll need over at the original XDA thread by rolle3k. And always use caution and use at your own risk!
[Via XDA Developers]