First off, I want to say that Sun assisted greatly with MySQL 5.1. I think it is a much better release than it would have been with MySQL AB doing the release. I do think this will continue in the future from everything I have experienced and seen so far. Sun knows how to make solid software.
So do I think that 5.1 was released too early? Not at all from my experiences of the MySQL releases. 5.1 is fairing quite well, and I think everyone that has a reason to upgrade to it (such as less locking for InnoDB auto_increment, partitioning, dynamic logging, etc...) should certainly start the process of doing so.
MySQL 5.1 is in quite good shape compared to my experiences with MySQL 4.0 to 5.0. As a chart of my experiences:
|Release||GA Version||My first recommended version|
These versions aren't based on exact bugs fixed, but based on interactions with many customers using the versions and various issues being experienced. It has a bit of gut feeling involved too, so it certainly is not a pure scientific method for determining this.
Also by no means is MySQL 5.1 perfect. There have been some pretty big bugs found and some annoying ones too. However, overall it has been working pretty well for most users.
I still do recommend you do test out all new functionality to ensure it works for you as there are many limitations. However, I would say that for any major software upgrade with any database system, this isn't specific to MySQL or the 5.1 release.
So go ahead and give 5.1 a try-out if you have been on the fence. Have a look around and kick the tires and be sure to report any bugs you find.