I initially had problems with my yahoo email (free version) notifications, but I realized I wasn't exculding it in my Task Killer. Since I fixed that, I've been getting yahoo e-mail notifications almost instantly. You've probably already done that, but just thought I'd mention it.
I do however have the same problem with the hundreds of sent e-mails in Sent box. It's a PIA! From everything I can tell and have read, though, it's a yahoo issue. I'm more likely to switch to my g-mail account as my regular e-mail than I am to switch phones or carriers. The phone works great for me in every other way, and if yahoo is simply not wanting to cooperate with a competitor, then I don't want to deal with yahoo!
I do however have the same problem with the hundreds of sent e-mails in Sent box. It's a PIA! From everything I can tell and have read, though, it's a yahoo issue. I'm more likely to switch to my g-mail account as my regular e-mail than I am to switch phones or carriers. The phone works great for me in every other way, and if yahoo is simply not wanting to cooperate with a competitor, then I don't want to deal with yahoo!