I've looked at several packages, I don't need anything overly complicated, it'd just piss me off anyway. But one thing I see missing is the option for 1 client to have multiple packages and transactions.

Here's a very typical scenario:

Client signs up for web hosting to "feel us out"
Month later, client registers a domain
signs up for another package, yearly this time now that they're pretty sure the support is good

I've got several customers with 3 or 4 domain registrations, and 4 or 5 hosting packages to their account.

Recommendations are appreciated else I'm gonna write my own as much as I hate to :(