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?
Short periods of time, especially with lower hashpower, can be highly variable. I think most people are seeing more like 0.01 per day per Mhash. I know I am. For the last few days middlecoin has been ~5% better than mining litecoin for me, which is disappointing compared to how it used it was during the peak of the dogecoin craze.