[development] Custom registration process

Hello to you all I'm needing to add quite a few fields to the registration process. Is the native login / registration process easy to amend or would you recommend using webform and building it from the bottom up so to speak. It's seems crazy not to use what's already there, but I cannot see a straightforward way to add to it. What have your experiences been? Many thanks Stewart -- http://www.flickr.com/people/mrbirch