I've also got a black granite bench top which I bought off ebay - well the slab at least. I got 2.8m for $850 and had a stomemason cut and fit it. If I was given a choice I would not have got black because as previously said in by olive it shows every single crumb, mark, grease spot and wipe mark. When spotless and polished it looks great!! (ok now lets get back to the real world). I have had light coloured stone bench tops and they are so much better as you don't see the crumbs etc as much.
As far as caring for granite it is no different than a laminate because they will get stains, heat rings (from extreme heat like pots etc). If cutting boards are not used then you will get scratches etc, have seen it many times.
For my next house I will probably get composite stone as it is supposed to be heat proof, scratch proof etc. The only thing I have not looked into at this stage is the (potential?) toxicity of it. What is the resin that is used? Does it off-gass or leach chemicals?? These are things I need to look into before making a final decision.
If you are after good quality stone bench tops at a cheap price then I can highly recommend fowls auction house (I have also seen brand new whole kitchens go for under $1000!!!). They are in the middle eastern suburbs and well worth the visit if you can get there. I think they hold their auctions on a Tuesday, best to check their website.