In all honesty, I've yet to really be 100% disappointed by a Final Fantasy job system. I've enjoyed every one I've played so far. If I had to pick one I didn't really catch on with it's probably XII. I agree that a lack of limit breaks adds to this, but I just ended up cycling my characters without any real regard for who they were. Perhaps at the very start I may have favoured Penelo as a mage, or something similar to that, but it's only because of the way the licences had panned out at that time. Once things got to about half-way point, everyone's licence boards were relatively full and it wasn't much of a challenge anymore. Run around, hit things, gain experience, move on. I didn't pay attention to what characters I had. That's probably a very bad sign for an RPG battle system, now that I think about it. In VII and VIII I paid attention, but only because I liked certain characters and their general feel in battle.
For pre-determined jobs such as in IX and X I really enjoyed being a bit more tactical for the most part. As time moved on, sure, certain jobs became less obvious but I don't think to an extent that they were no longer relevant. For example, if I knew that a tough enemy was weak to magic, I wouldn't think twice about drafting in Lulu immediately. To not do so would be insane for me. So that tells me that the jobs were still noticeable.
FFV remains my overall favourite job system. It is, as Murd pointed out, still a carbon copy system... but it's so damned fun.
The one thing I'd love to see is a modern FF using customisable pre-determined jobs. In other words, you do choose the jobs, but they are fixed once chosen. I think that would allow for a lot of replay value and I don't recall seeing such a thing in modern JRPGs. Please let me know if you know of a good JRPG that uses such a thing!