I have an '05 Rubicon and, like has been said, is a great platform to build on. The straight six is an awesome engine, but it will get worse mileage than the V6 in the JK. The Rubicon package, even without any modification will handle all but the most knarly rock crawling. It's nice knowing, even on moderate trails, that you have that extra edge in case you need it. Once again, just one man's opinion. It's also an extremely proven platform, which isn't meant as a slight to anyone with a JK, just saying the TJ has a ten year proven record is all. And the 04' is a HECK of a lot cheaper than a NEW Ruby. Give it some serious thought.