I totally dig Yahoo's new email beta version. I do not dig at all how aggressive they are with their advertising. Every email I look at or send there is an obnoxious moving advertisement. I find it interesting when I compare that with Google's gmail.
Google's gmail is not as visually pleasing or as easy to use as Yahoo's new beta version but it has very little if any screaming ads. Now it may be that the development of the new beta site requires funding from advertisements but still it's overwhelming.
All this being said, I still haven't been able to fully make the leap over to g-mail. Primarily because my isp is sbc global. I think if Google could plus up it's interface I would probably take the leap.