Yes, try, unless absolutely nessesary, not to touch the controllers (UserController/UserInfo) because the upgrade will wipe out your code...and then it can be a pain to put it back and it might not work correctly...

Option B, might work, if you inherit the "Info" class you might be able to add on to it, but you will still have to update the Controller in order to add the fields to the db.

I had the same issue...What we did was buy a module called "Dynamic Registration", in which you can create a registration form with any amount of fields and you can map the fields to the core field or a new custom field can be created.  We liked it until we wanted to update it for what we needed...No offense to the developer, but the code might have be fine a long time ago (v1) but it has been added on to so much the code is very "spagetti" and very inefficient.  What this module does though, is even know it is mapped to a core field (say "First Name") the module keeps a copy of the data in its table also...So there is double user data.

So we ended up creating our own module based on the same idea, but to suit our needs better.  I wish I could sell you our module, but it is an "in-house" only module.  I made it so that you can use core and custom fields, but when storing the core fields, they are only store in the DNN User tables and the only data in my tables were any custom field responses.  Follow me?  I also added on field "visibiliy" so the user can show or not show the data to other users on the "member profile" page.

So the long and short of it is...
If you don't think you will need to update the code a lot and you need it right away, go buy the "Dynamica Registration" module.

If you want total control and you have time, build it.

Hope this helps ya a little

If all you want is history - you might add some database triggers on the table you want history for that updates an audit table on any change.

otherwise, you'll be creating two different things:  A profile provider, and a User page.

For the profile provider, you can do anything you want, then change out the line in the web.config to point to your new provider.  it needs to conform to the expected signatures - not too difficult to do.

For the user page, it's a bit tricky because it needs to be one single module that handles:  new user registration, profile updates, password changing, subscription changing, admin edits of user accounts....   you can pick apart the one thats there to figure out how.  If you email me privately and are not in a competing industry; i'll send you the code that I've written to create the user registration seen at http://www.skydivechicago.com.

Beware - it's not a two day job.  It took me about a month of work to really get everything down (granted, the project included a lot - cross application login took a lot of the time.)  My code might save you a week of time; but the down side to how i do things is that it isn't 'configurable' after the fact - changing registration would require code changes.

If you decide you want to hire the work out, look me up; i've got a bunch of experience in that area of the code and so my time estimates are likely to be shorter than most.  Or if you just want a boost; we can spend an hour or two on a netmeeting and I can give you a 'tour' of what I had to do and why.

Cheers