The fees (as I was shopping) seem to end up being fairly standard. Some companies would seem to charge more in one area of service than another and in the end they seemed to come out fairly even. Do shop fees of course and also shop value - like you would with a Realtor in a buy/seel scenario.
In the end the property management company that understood me and my goals the best and then projected their care of those goals was the one I ultimately was satisfied with - BTW, they were few and far bewteen back "in the day".
Hope this helps.
Reviews for a Property Management Company are important, so definitely don't ignore them. In addition to reviews, I would sit down face-to-face with the manager who will be assigned to your property, or at least have an interview with them over the phone or using Skype. Get a sense for how much experience they have before you hire them.
You'll also be able to get a sense for what their motives are. If you get the feeling that your prosperity and the healthy condition of of your property are foremost in their mind, you should hire them.
If you are in the Boston Area, I have somebody I can recommend provided you have not committed already to somebody you trust.