Youtube applications seem to be gaining popularity as of late. The newest one on the block is called Vision and is developed by Metova, who have helped design the upcoming Xobni application as well as Slacker.
After having seen this posted over at BerryReview I decided to give it a more detailed look because some of the functions built into the app rather interested me, specifically, the ability to choose what video format hosted by Youtube you are actually wanting to view. For the most part Youtube videos on BlackBerry devices look rather, well lets be honest, terrible. Youtube chose to use 3GP compression for the "mobile videos" and lets just say they are truly not optimized for quality. 3GP does have the ability to look good when it's done right, but to save on assumingly bandwidth costs Youtube converts the source video files very poorly.
One exception to the "mobile video" rule within Youtube is the iPhone, so for the most part you will often hear people say "does it look as good as the iPhone versions?" This application is a step toward being able to say "Yes it does." The application allows you to choose between the poorly encoded 3GP files or the somewhat higher quality MP4 versions hosted by Youtube and it does it all within a nice, functional UI that even works over WiFi. Vision has been tested working on my Storm, Bold and 8900 and claims to work on any device 4.3+ so if Youtube videos are your thing be sure to check this application out and share your thoughts on it in the comments. For now the application appears to be free, but screenshots on their site indicate it may eventually be a paid application.