Membership Ease -
http://www.membershipease.com/

I looked at quite a few membership solutions and settled on this one.

Good:
Cheap
Very easy to use
Can use on multiple sites
Desktop software that installs all the files for you
Give automatic access to customers
Encrypted pages work with Paypal and Clickbank, other merchants use a non-encrypted page.

Bad:
Even though it's a desktop app, it connects to their site, so they have your ftp password info. I just changed my FTP password after installing and don't think it's a big deal.

Doesn't automatically remove people if they cancel a subsription.

If you go to the sales page it's $27...But if you try to leave the page they hit you with a "please don't go" special of $14.95.

It basically protects an entire folder, so you can use it in many ways, such as restricting downloads.

It isn't perfect, but for the price and ease of use, I like it a lot and think it's one of the better deals I've gotten lately.