[Paul M]

Originally Posted by fenderbob

....then I'd forever be trapped in the vB5 version I was using at the time the mod is implemented. In other words, I could never upgrade after modding my site. This is obviously far from ideal.

Is this still true?

It's never been true.
You may have to update some from time to time, thats always been the case, even with vB3 & vb4.
vbulletin.com has a number of extensions installed (since it went live with 5.0.0) and I think ive had to update a couple of them in the last 4 years.

Originally Posted by fenderbob

What about the hooks system? I get the feeling that the hooks system is used for the purpose of modding a site.

Thats exactly what its used for.
Its quite new in vb5 (prior to that you had the extensions system, which still works).
As far as hooks go, you may find they dont currently exist where you need them, but you can add them your self and then request they be added to the core.