[Sarteck]

I would suggest NOT upgrading unless you need new features presented in 4.2 that don't exist in 4.1.11.

From what I've read, there are some bugs in 4.2.0 that really need some ironing out, including some that can lead to slow queries, etc. I can't point to exact bugs in the tracker, because I haven't bothered to look--I have 4.1.11, it works for me, and I don't see anything in 4.2.0 that makes me go "OMGGOTTAHAVEITRIGHTNOW!"

I think advice like that Brandon Sheley is giving, to always upgrade to the newest available software, is very poor advice.

If you think that there are features you'd really like to see on your forum, I'd suggest making a backup of your forum, "restoring" that backup to another location for testing, and upgrading the test location, just so that you know what problems you'll be running into. If you are heavily modified, as you say, you will almost certainly run into problems, after all. :P

That way, you can decide for yourself if it's worth the upgrade, and know what issues you'll be facing when you do decide to upgrade.