WordPress 2.9, IMO, was released too quickly and is still rather buggy. There are some rather unnecessary requirements like “enabling” the post thumbnails before they work. However, major issues are the breaking of RSS widgets and more importantly the failing of the cron. I’ve had this problem when scheduling posts, and it is simply frustrating!
Anyway, the link above has a set of files that will patch these errors. So, give this a shot until WP2.9.1 is released.
Two simple pieces of code that allows you change the frequency that feed readers check your blog for posts. If you are not a regular blog poster, you can reduce the load on your server.
On my VPS, my sites are backed up every alternate day. The use of a WordPress database backup plugin just increases the load on your server. However, you can setup cron jobs within your hosting account to help you backup your database.
mysqldump -u dbusername -p dbpassword db_name | gzip > /home/cpanelusername/yourfolder/mysql_backup.gz
Still more examples on the use of the new WordPress 2.9 feature
Mark Jaquith gives you the lowdown on the new thumbnail feature