I bought 2 hashlets by 1MH just to try it out. The payouts for ZenPool are abnormally higher than mining any altcurrency. My best calculations show a ROI within 50 days, which is better than any currently available, or even proposed, miner (but only if you use ZenPool). So I'd be a bit weary of all of this, as it looks too good to be true, but I think I can risk for another 25 or even 50 MH, while they are still paying out. Who's to say it may even truly ROI 
A note of caution: You can't sell your Hashlets. So once you've bought them, that's it. There is a proposed "market" for buying and selling (I suppose something akin of CEX.IO) but it's in the "upcoming" section for now.
A note of caution: You can't sell your Hashlets. So once you've bought them, that's it. There is a proposed "market" for buying and selling (I suppose something akin of CEX.IO) but it's in the "upcoming" section for now.