I like that you recently added the option to switch between accounts, as my husband and I both have email accounts through Yahoo!, but I've always found it a pain in the neck to have to log out, log in, check the account, log back out, log in again. I was also having a recent issue that seems to have been resolved where when I'd go to switch accounts, if my browser page wasn't full screen, I'd end up with an advertisement covering my name up top and I couldn't do anything.
With that said, I've also had several issues. I tried to send some pictures to a NASA employee today, as I went to Stennis Space Center in Mississippi recently and she was looking for some images from the workshop. I could only send 5 at a time because my zip file was still too large to send via email (if I was lucky) so I had to create a dropbox account, which took about an hour total to add email addresses to share the images with and upload all the images. This is my second Yahoo! email account, as my first account was linked to one of my previous friend's from high school, and she kept sending me explicit content that I had no desire to see. Despite adding her to my spam list, her emails kept showing up in my inbox. I couldn't figure out how to delete the account, so I just changed the password by typing in a bunch of random letters and numbers.
Further, your Terms of Service are written in such a way that they completely cover any issues you may have, because the average person does not have a lawyer and a dictionary present when reading through them. While it's great to have a "save your ***" version available, make another, more simplified one that most people can actually understand, with a link at the bottom to the technical one that is full of jargon.
I prefer to use a web browser to view my email, regardless of provider. I do not own a cell phone of any kind and do not wish to get one. The biggest issue that I have had with Yahoo! mail is that, when I zoom in on any emails, the page gets distorted and harder to view. I am visually impaired, so being able to enlarge text is very important. I am almost legally blind in my left eye and rely heavily on my right eye for vision. It gets tired after reading for about an hour at size 12 font, so I start increasing my font gradually over the course of a day. By night time, most of my screens (whether it be textbooks online or word documents or email) are at approximately a 48 or 72 font, to allow my eyes time to "rest" a little and not have to strain so much.
If I could find a reliable email host who provided free accounts, allowed for more space to send pictures, videos, documents, etc., had a better spam filter, had simplified terms of service and privacy policies, and most importantly: had emails that did not distort when zoomed in, I would switch. I have an account through Google, but find this to be more convenient as I use it for all of my school contacts and the username mimics my college email address, which appears more professional to potential employers.
Update: I actually forgot.. the Yahoo! Answers anonymous feature doesn't actually work. I get emails as soon as someone posts an answer to my question and it gives me their username, which can be clicked. If they decided to post anonymously, I still know exactly who they are, which defeats the entire purpose of anonymity. I know that, since I can get emails on who posted to me, it works both ways. If I prefer to remain anonymous in regards to my answer, I can't answer the question.