Does the vbulletin paid subscription feature produce income reports, demographic reports, etc for an administrator?
Does it send out multiple welcome emails, instructions, etc when a user signs up automatically? Does it offer an offline payment type so that people can subscribe and pay by cheque?
There are a multitude of features that make amember a very good script.
Vbulletin out of the box does not provide those features. But, we can always add them in. I'm not knocking your script, but I think that people who don't have the extra money can have bells and whistles with the subscription service too.
I agree that Vbulletin is very weak on reporting tools when it comes to subscriptions.