Some suggestions:

1. Instead of emailing from your server, how about sending email through the user's server?

2. You already allow switching of coins based on profitability, could you add the ability to switch to the next profitable coin if no results are being generated or if there is some other problem preventing  money from being made on a given coin? Sort of like coin failover?

3. Ability to disable a profile so it is not mined on, even if it is most profitable.

Thanks,

tejsei