I think it really depends on your content and how you get and curate your list(s). They just really want to make sure people are opt-in, I think. I don’t have a ton of affiliate experience with them, but I know if you ask them direct questions they’re happy to give you a straight answer.
As for Madmimi, I like the simplicity. It doesn’t have a ton of complicated stuff for setting up or making the design, yet it has a lot of add-ons you can switch on and off on a whim. Madmimi has also shown a great deal of support in my limited experience with them, so they’re a really easy recommend for users who don’t want a lot of extras.
Mailchimp doesn’t like it if you put affiliate links in a large number of your mails. But that doesn’t mean they forbid you to do so. As long as you keep it natural there is no problem. It’s perfectly fine to mail an affiliate link now and then. Unless your intent is to spam people with affiliate links, I wouldn’t worry about it.
I use mailchimp but will be switching back to aweber. Mailchimp is good, but aweber is better. If you are starting out mailchimp is probably the best option since it’s free 🙂