I would think that you should read the FAQ over at the singlespeed forums on MTBR and then post most specific questions.
My suggestion?? Borrow someones bike and go for a ride and see if you like it.
Also.........I don't think if I would get a dedicated singlespeed (horizontal dropouts, no derailer cable routing stops, no derailer hanger) if it was my only bike.
For those of us with way too many bikes that is not a problem. If you have but one bike and are not Matt Chester you might need something more versatile. A hardtail with gears is the most versatile creature there is in my opinion.