Thanks for your reply Crocko.
There's no way that I've made any return on investment from the two usb asic miners yet and I'm not entirely sure that I'll actually make any back on what I paid for them. I was more interested in getting started and as I don't factor electricity costs into my calculations, the way I see it is that any bitcoins I generate is a plus as I'm not looking at these as an 'investment', more a way to climb the learning curve.
If you go out to dinner and spend $100, you don't think, 'Hey, what's my return on investment for that $100?' You have a nice meal, probably a bottle of wine, hopefully some good conversation and you enjoy yourself. I bought the two usb asic miners for enjoyment, so anything I get back from them is pure upside. Like I said in my post above, I'm not mining as a form of investment, I'm mining for enjoyment and to learn more about the world of bitcoins.
However if you are looking for ROI information, check thegenesisblock.com here:
http://mining.thegenesisblock.com/Select the equipment that you are considering buying and it will give you a calculated ROI on the item. It seems that the calculator appears to work on how many blocks that you will actually find and that's probably ok if you are mining solo and not joining a pool. I'd imagine that the numbers would be higher if you mined in a pool.
Another ROI calculator is available from bitclockers.com :
http://bitclockers.com/calcI'd suggest you be very careful and use the difficulty factor from thegenesisblock and make sure that the watts you type in to the calculator are correct. It seems that the calculator hasn't been updated in a while, but it's useful as you can change variables (like zeroing the electricity cost) to give a more personalised answer.
I started off cpu mining with 50btc using their 50miner software, it seemed to work ok but my cpu was so slow it was worse than watching paint dry. I made the decision to buy some specialised asic mining gear but what your find almost immediately is that although plenty of places advertise it, most of it is either available only to pre-order or you pay a very high price. I wasn't interested in paying a high price, so I pre-ordered a 7ghs Jalapeno from Butterfly Labs which will arrive sometime in the next year and to get started I bought two ASICMiner Block Erupter usb miners, one from Amazon and one from Ebay.
Right now I'm using two usb asic miners, each give a nominal 333mhs (very low I know), I'm using Bfgminer as mining software and I'm using BTC Guild as my mining pool (
www.btcguild.com) and it runs smoothly. I've another two usb miners arriving soon to double my hashing to 1.3ghs and will continue to buy more usb miners in the future. BTC Guild also sell usb asic miners for 0.24 BTC each and I've also seen them on this forum for as low as 0.2 BTC each for a minimum order of 50. Look around, see what's available but it's worth spending time getting a feel for prices, there's the usual scammers on ebay and amazon trying to sell them for 100-500% more than they cost, so know what you're doing and what you're prepared to pay before you part with your money or bitcoins.
It's worth keeping an eye on the news, I use these two news sites mainly:
www.coindesk.comwww.thegenesisblock.comTake it slowly, do your research. Enjoy the journey