i've used nxt the past year. overall i like it. the price is high at around $14 a bottle, but it is applied in very thin coats so one bottle can do 8-10 waxings of a crossfire.

i found it very easy to apply with the included sponge applicator. it smells good too. as stated already it's not a cleaner wax or polish, so it isn't good for removing contaminants sticking to the paint. but it's fine for a surface that is already in very clean condition. it's nice that you can apply it to the entire car at one time. it is removed easily and doesn't create any of the chalky dust that many waxes and polishes (like nu-finish) will leave behind. i remove it using a cotton towel and have noticed that after wiping the dried wax away initially the finish will look a little "greasy" or "waxy". but after buffing with the towel back and forth a couple times any residue is removed and the finish will look great. as far as longevity is concerned, it's really hard to tell. my impression is that it lasts longer than meguiar's gold wax, but i've heard some say it doesn't last as long. but how in the world can you tell? it seems that some of the slickness goes away after a few days but that doesn't mean the wax still isn't there protecting. i've been applying a coat of wax every 2 months or so. as far as filling in fine scratches, nxt claims to be able to do it. my impression is that it does to some degree even though there will always be some deeper swirl marks. i've never seen a car finish without some swirl marks. i'm not sure it's even possible to eliminate all swirl marks without seriously degrading the clearcoat thickness.

one thing i'd like to see is what happens if you were to expose identical car finishes treated with different polishes/waxes (applied at some interval) to the same elements for a lengthy period of time (say 5-10 years) and with a control sample without any treatment at all. i'd bet some cars have durable enough paint that you'd be able to clean them all up at the end of the experiment and apply any old wax and the finish would look good. on the other hand, i'd bet that some car finishes would look pretty bad no matter how often you polished them. in some cases the clearcoats are probably so soft that simply drying the vehicles and applying/removing the polish or wax will do damage.