Yes, I have worked for them for years. They pay on time and the reports are easy.
No. You have worked for some of the MSCs which utilized the iSS platform. Those firms may have paid you on time, but iSS did not pay you at all. And there is no reason to infer that one MSC which utilizes iSS is as creditworthy as another firm which uses iSS.
Do you know if iSecret Shop is a legitimate company?
KellyMac, can you tell us why you ask? The reason I question is that it would be unusual to get a solicitation from a company with whom one did not sign up (red flag for scam!) There is a legitimate company called isecretshop, but it is a software platform rather than a mystery shopping company, so shoppers do not perform shops for isecretshop nor are they paid by isecretshop. If you were contacted by a company called iSecretShop and asked to perform shops for them, it is likely a scam. If you were sent a check in advance of performing any work, that is almost certainly a scam. If payment offered is more than $25, it is likely a scam.
So, the quick answer is Yes, isecretshop is a legitimate company. But, depending on why you are asking, the iSecretShop you are dealing with may NOT be the legitimate company and you are perhaps being scammed. You didn't provide enough info to know which.