Suspension is rough but not uncommon for vehicles that utilize 4wd. Fuel economy is great (I get 18 mph) and that is with a hole in the exhaust manifold. The power is fantastic. I live on a ranch in NW North Dakota where we have some pretty tough hills; the 4 WD of the QX4 really kicks, even when chasing horses, cows, straight up some pretty tough hills. I purchased it with 86K miles on it; it now has almost 150K miles and the engine's never been touched and doesn't "burn" oil.
Had this vechicle for about 3 years/30k. It was reliable, and maintenance was not bad. Ride was a bit stiff, and MPG was terrible. About 14-15MPG. 3.3 V6 struggles badly to move this heavy SUV. But it was a nice luxury SUV, and in the snow, it was among the best. Great winter vehicle. Radio went out, starter, and some other minor things, but no big deal. My full size Tahoe gets better MPG and with a lot more power.
I bought my 1997 Infiniti Qx4 in '99 (I'm the second owner) and this is the best car I've ever owned. I will eventually give it up, but my goal now is 300K miles because the engine is that good and reliable. Drives very well for what is essentially a truck (a little bumpy in the back seats, but my kids have never complained). You can haul a lot in it, too. And in the snow, and on mountain passes? This SUV can cut through anything. I've only used 4-low a few times, mostly I just hit the switch for 4wd -- and you can go anywhere in confidence. Only repair? Alternator replacement at 140,000 miles. If you find a decent Qx4, even if has over 100k miles, grab it. I don't plan on giving mine up anytime soon, though. Plus, it's got a killer six-speaker Bose sound system.
My brother bought this SUV in 1995 and ran it up 40k and did a quick sale to me as a fixer upper for $1000, he was told from a shop that it would cost $12k to fix right. Nonsense!~!Well $1200 later she was purring and looking new, but you have to look at the estimates! They priced everything as infinity and tried to charge dealership cost plus shop markup! I shopped pathfinder on ebay and cut the bill. Then gave it to mom, she's in love with her qx4 and even had the stereo upgraded with a new stereo with back up camera and DVD has been flawless for another 60k miles and climbing. She says it isn't how old you are, its how your treated.
There is a reason the QX4 is a very high demand SUV. I have joyfully driven this vehicle for over 150k miles. It purrs like a kitten and is as dependable as the day is long. The QX4 is the best vehicle I have ever owned and it pains me to part with it. However my new purchase is also an Infinity SUV. The QX4 is an expert handler on snow and ice and superb craftsmanship is still evident 150k miles later. It is a tad bit underpowered for mountain driving and the gas mileage is below average. However even today the vehicle turns heads and is an absolute joy to drive. It is too bad Infiniti discontinued the QX4 as I would certainly have bought another one. Viva QX4!! I will miss my trusty friend.