If you do it honestly there is no problem.
There's a guy here in WA who talked in details about that aspect. Maybe it can answer the kind of questions you can have about it: Introduction - New Views on Reviews

Yes - In fact that was taught in one the training here in WA.
I would suggest to search if reviews of the program has potential traffic because if you write a review that too little or not being searched, it might not so beneficial to you.

Write with intent.

:)
jOe

hi Kerry

I don’t think I can give you a definitive answer to this but I can give you my opinion.
Clearly this idea could provide some good content and be very valuable to you customers. I like the idea but think that you would need to find a way to do so without having to sign up to endless programs which may or may not cost you a lot of money. If you search google for affiliate reviews you do get a long list of marketers that are doing exactly this so either there is a saturation within that niche or they are doing it because it is working, in my opinion that is always a difficult question.

Hope this is some help but if you want to bounce ideas I will always try to give you a valuable opinion.

Drew.