I haven't though a few on the forum have, I would again vote for the Sigma 30mm. You keep your AF which is important for most street shots, Sean on this site is a huge fan of this lens.
By the middle of the year you will be able to buy, hopefully, the new Canon 24 or 28/2.8 IS, that will be a wicked lens. For similar dollars you could get the Zeiss 35/2 and belong to an exclusive MF brotherhood.
With all lenses you get what you pay for. The Rokinon will be definitely worth the money, but not in the same class as the Canon, Zeiss or even the Sigma (if you get a good copy and I think now days you tend to, I love my Sigma 85mm).
Bodies will come and go, but good glass lasts.