Hi Jillaine,
We currently use the membership module to track our different levels of members and I will admit that I am less than thrilled with the module. However, we are a cultural organization where a membership is more like a season pass than being a member of world wildlife fund or planned parenthood or any type of association. So my complaints about the module might not be things that would be a problem for you.
A few issues:
1. there is no way to track the history of the particulars of the actual membership (you can track the history 'level' but you can't track the particulars of historical memberships like names on the cards, how many children or when the cards were printed for past memberships - frustrating for us).
2. we can't seem to clean-up old membership card levels - i.e. the historical info in a person's record indicates that they use to be a 'Toucan Family' level member and then became a 'ZooKeeper Family' level member, but that doesn't mean anything to us as that was 10 years ago. My membership manager wants to be able to change the names of those membership levels so they match levels from today since no one around here even knows what Toucan Family level is... but we can't.
3. we are also having a problem with the calculated field of Years as Member and Consecutive Years as Member in that they don't seem to be taking into account the years the person may not have held a membership with us... we just realized this last week when we were running some analysis on member retention so we haven't researched it yet, but it makes me a little upset...
4. we are using export to get our membership card information out of the system to send to our mail house because the Mail tool doesn't give us all the fields we need - not that big of a deal I guess, but it is one more step.
Sorry if this sounds negative... Hopefully someone with more postive experiences will reply to balance my opinions out.

(and maybe someone will tell me how to fix my historical membership names too!)