Really cool investment calculator at the above link.

Experimenting with various deposits spread out over three self-referrals (i.e., using my own referral links) it looks like the best average return (total return/total investment) is 20% and regardless of how you spread out the investments it will take something like 79 months (6.5 years) to get the full return.

On an annualized basis this works out to be 2.78% APR. (That is, if you invest $100 today at 2.78% APR in 79 months you will have $120 or a 20% return.)

This is not bad considering today's savings account returns but it's awful as an investment, especially one with any risk attached to it (as this one does). The only way it makes sense is if you believe you can get other people to use your referral links. It doesn't work as a stand alone investment.

There may be good reasons for using Pyramining, but I would look elsewhere for investing if you're looking for a decent ROI.