I started out with Corporate Research. You are all right about the poor pay. MSers have to be careful to consolidate trips for assignments in order not to be paying the MS company! I carry a small dry erase board in my car. It's the kind the teachers attach to the wall for writing homework assignments on. When I have a bunch of shops in one day with photos required, I photograph the board with the assignment number and place, then I do the shop photos, then photograph the board for the next shop, etc. It saves time trying to remember when I shop started and another stopped, especially for convenience stores when I may not have taken the photos in the same order that they are listed in the paperwork.
CRI has one shop that I like. If I explained it in detail, I probably would be giving away too much proprietorial information. It is medical, there are no photos and the pay is very good. It also lets me return frequently. I doubt, though, that it is available in most cities. With any company, you have to look for what you want.
The main thing for me is the nuisance of having to upload receipts and photos. Some companies let me fax or mail, which actually take more time, but my computer is old. My computer won't upload, so we have to do it on my husband's computer while doing the report on mine. We have some new equipment but haven't had the time to install it. My husband works weird hours, so I don't schedule anything with CRI unless he'll be here to assist when I'm done. CRI is strict about deadlines (midnight!--why not just before 8AM?) but flexible when there is a problem. I get the impression that their schedulers are overworked. I like the frequent pay.
Some (most) companies need to itemize their checks, though. It helps to know exactly which shop I am being paid for. If the pay is by direct deposit or PayPal, why can't I get an email telling me what the payment was for, not just that the payment was made?