its not bad I guess, its dustcoin minus a few features. But meh...
Add support for all currency's that Gox uses - %55.55 out side US to my site
Try not to use coinchoose as a data source - single point of failure - short term not so bad just cache his data? long term is bad very bad (if he decides to close permanently your stuffed)
Try to use as many exchanges as possible and locally store the data - they go down a lot
Try to add power costs like dustcoin
Edit: you had me scared there for a minute (with the title) thought I had a direct competitor
(call it a mining profitably calculator)