Bookings API versus existing spaghetti code I'm working on an appointment booking system that allows registered users to book an outcall with an agent.

I've only come across Bookings API and Public Bookings, which seems more for things like library work rooms than it is for service industry people -- and even then, nothing about it looks at all pretty (Not a knock to the devs; it just isn't at the point comparable software is at on other CMSes.). My client has an existent system coded in some pretty funky PHP -- nothing OO, all logic code is in the same file as the design code (which is in, get this -- tables. Everything. In tables.) -- and I'm currently thinking about porting it to Drupal.

My questions are thus:

a. Are there any alternatives to Bookings API for appointment booking?

b. If not -- and considering I don't have a ton of Drupal programming experience -- would it be more worthwhile to update the existing spaghetti code appointment booking system to function as a Drupal module, or more worthwhile to just make Bookings API function more eloquently in this usage case (considering it has a lot more functionality, hooks, etc. than I could probably program into a new module in a short time)? 

Thank you!
In answer to part (a) there is the Resource Conflict module, which appears to be similar in goal to the modules you mention above.

As for part (b) I'd argue that it is typically better to update or replace custom spaghetti code in such a way to work with existing modules--doing so will greatly ease the work of future maintainers of your code, and allow it to benefit from future enhancements to the Bookings API.