I have one of those "nifty fifties" as well and yes, it's really a great lens for the price. It doesn't really focus any faster or more accurately than my Tamron's, but hey...for $85 who can complain! It's sharp and that's the most important thing. The one thing I will say is that if you go to do anything like portrait work with it, watch your DOF...it can get really shallow, really quick!
As for "wide angle adapters", while I've seen a number on Ebay, the couple that I've tried are...well...pure crap (and you don't hear me say things like that too often). Aside from a serious lack of sharpness, most of them really seem to cause a lot of problems with aberrations and such...ghosting, colors out of whack, etc..
The thing that makes the nifty fifty such a great little lens is that it is so sharp...most of those screw on adapters are going to take that away. Some of the pricier models that are actually made for video aren't too bad, but most of the el' cheapos aren't even worth using as paper weights. In fact one that I had ordered on Ebay was so bad, I had it back in the box and back off to the seller for a refund the same day I received it (and you don't hear me say things like that too often either!).
Just my ever humble $.02 worth!
"Wondrous is our great blue ship that sails around the mighty sun and joy to everyone who rides along..." - Jeff Lynn