Yahoo Mail used to work.
Yahoo has been sorely trying the patience of its Mail users recently.
More spam recently than I recall.
Account hijacking incidents.
Forced move to new version (which does have some good new features).
No longer support Opera browser.
New Yahoo Mail seems slow, not helped by ad panels.
Recent outages and very slow spells.
Yahoo now changing to SSL (probably a good thing) but this may inconvenience some users.
Help FAQs on SSL introduction only for Android and iOS -- no mention of WinPhone, Symbian, Blackberry users.
If the above continues to the extent that moving would be less hassle, Yahoo Mail is finished.