Ive been having some trouble with Tubemate, disconnecting during large downloads, not found errors, et cetera.
Ran into this site, not app, and you simply paste youtube url and it provides all available download links. 720p and 1020p if available. I mean its just like the apps out there except it has been much more stable for me. Plus I can just keep browsing online while downloading and jumping back and forth through tabs.
Tablet Youtube Downloader: Download and save any video to Any Tablet from Youtube, Dailymotion, Metacafe and more!
Just remembered, also works for google video, meta cafe, daily motion, and basically any site using the same setup.