I am using an AMD W7000 Firepro and getting 200Kh/s mining in an altcoin pool, which automatically switches to the most profitable altcoin and autotrades them back to BTC.
For a GPU, the results are pretty good - Im getting 0.001 BTC per day (although Ive only run it for 1 day). Block erupters are on sale for £60, and give 330Mh/s - over 1000 times faster. So from past experience 0.001 * 1000 == 1 BTC, which sounds great.
Any ideas what im missing here?
The coins you're mining, are they sha-256 or scrypt based? Purpose-built bitcoin mining hardware can only process sha-256, while a GPU is generic.