My 1.5 KH/s earns me about $20 a day here. The same power at LTC earns me $9. Seems legit to me.
Over the last 3 days I've got an average of ~0.0178 BTC per day. At today's rate that's ~$15/day, with 1.8Mh/s (about 1.3% rejects).
Would you mind sharing your address? I would like to see the difference in the patterns, if any?