BAD
very slow (with DSL), unreliable, servers down every two weeks, only 2MB for email storage, few services compare to Yahoo!, uninteresting extra options, spam filtering is a joke, adverts here and there. Non transparents policy concerning spam, .NET, or bill payment issues (you want to cancel you extre storage options? you have tp chat online with a pseudo support and listening to him\her convince you to keep the option, with Yahoo you just click on a cancel button)
GOOD
integrated to Microsoft softwares as a web extension.
Wit people would choose Yahoo!s reliability over Hotmail ridiculous persistence in building craps