If you are buying shares you better ensure they are registered with the SEC so if things go south you dont get screwed.
They are not shares of Cryptsy as such. They are only profit/fee "shares"...
Cryptsy is very aware of the difference between the two, as they are FINCEN approved in the US - registered as money transmitters, adn complying with AML and KYC regulations. As an example, only validated customers can trade USD with other coins on their site - the first one in the US. That is why I was considering investing in their profit/fee shares...
Anyone had bad experiences with them? Like not paying out or something?
A portion of your hyperlink states "securities" specifically, which falls under the securities and exchange commission (SEC). This is an entirely separate department from FinCen and completely separate from "know your customer" and "Anti money laundering" laws/policies. Shares are shares, regardless of how its worded. Personally I believe that if they are doing this, they should get an SEC license (unless they already have one, I dont know).
Coincidentally, someone sent me this today
http://altcoinpress.com/2014/12/bitcoin-stock-exchange-operator-fined-by-sec/As far as bad experiences, I have no personal experiences from this type of product they are offering. But I do have multiple bad experiences with them in the past in regards to trading. I used to operate a small multi pool, and every week there was an issue. 2 times off the top of my head, once they took a batch of coins that we auto sold and sold them 15 times over, later on once discovered forced us to pay for their mistakes. Second time there was over a week where I could not withdraw because the captcha text box was missing (yes, the box where I typed something in was gone) and I could not withdraw.