WordPress 2.9.1 was released yesterday to address some bugs which were in 2.9. In the announcement post Ryan Boren states that the scheduling bug has been resolved in 2.9 however the scheduled post I had set after I had upgraded missed it’s schedule so I had to install the Semiologic bug fix again. WordPress is a strange creature sometimes though with some people getting errors and others not, so you might be lucky enough not to have to install the bug fix.
It seems the blank page problem I was getting in WordPress 2.9 is fixed too. Earlier today, before upgrading, I noticed that a few comments were processing fine on my own posts but the blank page appeared when commenting on other peoples posts. I’ve did some tests and everything seems ok so fingers crossed we’re back to normal 
It’s always advisable to upgrade to the latest stable version of WordPress but I must admit that occasionally I’m lazy and don’t do it right away, particularly if everything is working correctly. However I would strongly encourage you to upgrade to 2.9.1 right away as WordPress 2.9 was particularly buggy.
Link: Download WordPress
Am I the only one who is unable to edit my templates from inside the wordpress admin? Haven't done it in a while so I don't know if it is a 2.9.1 issue or if it has been out for a while. Haven't found anything online about it. Can get around it but its a pain. Any related problems?
You need to make sure all template files are writeable in order for you to edit them via the admin area.
I’ve learned its usually best to wait until the extra .1 version with web applications (for example 2.9.1) and then wait a days after that is released until upgrading. Unless you have a really old version or one with security holes. Any minor bugs or forgotten files are usually sorted out once the majority have made the switch and reported back.