I've been on the verge of buying one several times but probably will hold off until I absolutely NEED a vehicle badly, but I've gone as far as visiting a few dealer lots and looking at ones I've found listed.
They are fantastic, my Dad has one which I ended up borrowing for a camping trip and I love the thing. In my case it's not a passing fondness of them, I've got seat time in them and have actually had to go about my day and travel in it, so I feel pretty confident it's going to be fine to live with.
Of course I already have a Nissan, and the Frontier is practically identical to my Xterra in power plant, drive-train, frame configuration, location of just about everything, and the interior. But I was surprised how fond I was of having a truck bed given every vehicle I've had has been an SUV. On that trip I had the Frontier, I was able to put everything under the bed cover and while on the road it was a clean completely enclosed setup which I liked a lot.
One thing I can't make my mind up on about them is if I like them with or without the roof rack. The OEM rack is cheesy as hell, it's functional but for it's beefy size it's flimsy and ages poorly in the sun.. I do like the FrontRunner rack for the Frontier. I think though if I had a Frontier I'd want the FrontRunner or no rack at all.
I will note my only gripe with the Frontier is I've noticed the auto transmission seems like it always wants to be in 1 higher gear than it should, I'm sure programmed that way to pad the EPA fuel rating. It delays down-shifting to the point you get this abrupt shift halfway up a grade that is somewhat annoying. It can be mitigated by being aware of it and hitting the gas a bit firmer and earlier to try and force the shift when you need it. It clashes with my much older 4runner's auto trans, which always seems to shift exactly when it should without much thought, you start to slow and it drops a gear without you jabbing the pedal. I can't compare to my Xterra because it has the 6-speed manual, which is one big perk of a Frontier in that you can still get a manual trans in it.