I bought into this a few days ago. I only bought 100 GH/s because I have this feeling that I wont really make anything on it. In fact I would be happy to see just break even in 5yrs. It all depends on the difficulty not increasing drastically I think. This term it doesn't look like it is predicted to be a big increase so I shouldn't see a big drop per day. If we get a few terms with bog increases I may not have any chance to ever make it back. Either way it will be an experience that I will learn from one way or the other.
Based on my experience, the payout from PBmining compares very favorably to the amount that I've mined so far using my own equipment at home. I began mining in early March of this year with a couple 22 GH technobit miners. Gradually worked my way up to 6 of those (120+GH). Now have a total of over 300 GH with an S1 miner. To give you an idea of the effect of the change in difficulty, my 24 hour earnings on the BTC Guild dashboard just reached over 0.01 BTC for the first time since mid-May, back when I had significantly less hash power. In April I started buying contracts at PBmining with some of the bitcoin I was earning from mining, and stopped at 150 GH.
Total payout from home mining through BTC Guild so far (early March to present): 0.74 BTC
Total payout from PB MIning so far (early April to present): 0.487 BTC
I think that almost all of us who got involved with mining bitcoin did not see the results we had initially been hoping for. On the other hand, a part of the lesson is that mining bitcoins represents only a very small part of the opportunities that cryptocurrency will open up for those who have gotten involved. Beyond simply hoping to reach ROI, you can appreciate the benefit of getting at least some baseline income of bitcoin which you can then use. Just enough to start making some small purchases. Thereby you begin participating in this new economy, and start thinking in new ways.