"the cognoscenti" ; am I the only one thinking about the Illuminati returning into the time with internet available?
The problem with the more obscure services is always whether they'll stick around long enough, they have to compete with massive multinationals... This has lead to the downfall or to becoming less effective of several email services that were great when they first came along (think Safe-Mail.net and Lavabit)
Other than that, I don't use Yahoo myself so I won't judge myself. I am still somewhat doubting though, not so much for email purposes itself but merely for Flickr. That is, if Flickr is more protected against hacks and thus safer than the email part of the Yahoo package. Otherwise I better stick to a paid photo gallery host. 1 terrabyte free photo hosting is tempting, but not if you constantly have to worry about the security of your portfolio.
(I don't consider Instagram to be a photo portfolio host, more a photo diary. A portfolio means photos are ranked per subject in folders rather than displayed in chronological order)