I recently switched from Typepad to WP hosted at Yahoo after Six Apart's inability to run stable services became apparent. To my dismay, things are hardly better with Yahoo.
My site was caught up in the database failure a couple weeks back, and now, it's simply slow as molasses (when it actually does load and doesn't time out).
It's incredibly frustrating to get this kind of service from one of WP's hosting partners -- that partnership is an implicit recommendation of Yahoo's service, and Yahoo appears unable to live up to it.
Yahoo's support is awful, its service abysmal, hell, even it's prices aren't good. I went with them because I'd assumed the WP partnership would reap some user benefit, but if it does, I sure don't see it.