As far as Cydia/Rock, I have had many problems with Rock. It DOES look smoother, and it SEEMINGLY works faster, however, about 2 weeks ago, Rock was the reason I almost lost my jailbreak. It was 'updated' with a bug that caused your iPhone to LOSE all available memory. The issue with that was that it was eating all free space, and messages would come up telling me to delete pictures, videos, and to uninstall apps. The problem is that when you run out of memory, the phone will completely freeze up, and force you to reboot. Upon rebooting, BECAUSE you have no memory, the OS ("operating system") would refuse to start.
It took every bit of troubleshooting that's I've spent the better part of a year learning to RETAIN my jailbreak and unlock, using multiple programs, multiple methods, working around multiple errors and all of Apple's bullsh*t.
All because of Rock.
Here are some other known issues with Rock.
-Rock Extentions does NOT play nice with Cydia's mobile substrate. They OFTEN (multiple times a week) will conflict and put you into 'safe mode', also known as "sad iPhone".
-Rock has broken the ability to watch movies and/or YouTube. If you watch videos, 1 out of every 3 videos will freeze and cause you to respring. This works with videos that you've recorded as well.
-Viewing your camera roll would also cause the same resprings from above.
Overall, Cydia is just better, and it has a larger database if you've added all appropriate sources.