I've heard the Commanders aren't selling too well and are probably going to be discontinued. But they're still fairly common on the rental lot I frequent, so here goes. 
From the outside, it's big. The Commander was obviously designed as a response to the success of the Hummer H2. As mentioned, it's success was even shorter lived (/non-existent). There are reasons for this, but first the most important question? How well does it fit a big guy?
For somebody 6'4, the headroom in the Commander was never a problem. Traditional leg room was also fine, the problem was with the width of the legroom... there's crap that juts into that space, thus into the sides of your legs, just like my own Jeep Liberty. But as I've become somewhat used to that, space wasn't an issue *for me* in the Commander.
It makes a pretty fair rental car, except when you have to pay for the gas you put back in, or if you need to negotiate particularly tight spaces. The Hummer influence on the outside is fairly obvious, on the inside it's more the H1's amazing feat of being a wide vehicle without having much breadth to the seats--the Commander also has a wide center tunnel, but it's not as ridiculous as in an H1.
The more annoying influence is the new Jeep chintzyness. Maybe it was always there, but the '02 Liberty limited didn't have it, nor did the high-end Jeep Grand Cherokee Limited. It's like they're trying to ape to utility of a Wrangler but it just feels all wrong in a $30-$45k vehicle. EVERYTHING inside is plastic, and the hole where the locks come through the doors is just rough-cut with a hole-saw, no grommet or anything. No, not a big deal, but it's an example of where a car that easily costs $40k misses the boat. At a glance, this feel seems to be present in the new Jeep Compass as well.
The Commander is nicely equiped in the electronics department, the nav-screen becomes a backup camera automatically, the built-in nav system itself was fairly functional (once I dug out the DVD from the glove box and figured out how to remove the plastic cover over the drive's slot), the backup distance warning sensor even seemed kinda useful. These are all features I'd not gotten to try out before.
The power seemed about what one would expect: plenty, but nothing noticably special for a vehicle of this size, price and considerable weight (a HEMI is available as an option). The transmission had a manumatic mode, but in this vehicle at least I don't think it's anything more than a pointless gimmick. Just didn't feel like it had any more point or utility than shifiting a traditional auto from D to 3 to 2 to 1.
So I wouldn't buy a Commander mainly because of the feel of the interior, but the only reservation on renting one again is the price of all the gas it'd guzzle. With three rows of seating it'd be great for transporting familly, and if you're not used to something this big the electronics make parking easier than you'd expect. So a pretty good rental and if you don't mind plastic cabin (or Chrysler / Jeep service...) you might be able to get a hell of a deal on a purchase. Especially if you know all the buttons to push.
