I have been using Yahoo! for my personal web-hosting for almost a year now. I also manage a few other sites hosted by Yahoo! and they have been relatively problem-free (not including the database crash I had a few months back).
When I started a blog on my personal site, I chose WordPress based on recommendations, reviews, and personal experience. One thing that I thought was great was that Yahoo! offers automatic WordPress software upgrade, and I chose that option. Currently my blog is still running WordPress 2.0.2 while version 2.0.6 was just released. I had contacted Yahoo! customer and technical support regarding the WordPress version. Unfortunately Yahoo! deems that there is no need to upgrade WorPress automatically, nor offers an easy to upgrade it manually.
Honestly I am a little bit “miffed” with Yahoo! on this matter. I have been searching for some documentations on upgrading WordPress using Yahoo! web-hosting. So far, I have found none.
I am currently running a mirror of my blog hosted by the good folks at WordPress.com and it has been generally excellent. One thing that I recently found out is that a little rant that I had might cause a little inconvenience with WordPress.com administrators.
Anyway, I am still looking for some instructions, informations, and feedback on upgrading WordPress using Yahoo! web-hosting.
The answer might lie here:
http://wordpress.org/support/topic/83231