Loose ball hubs are just like anything else that isn't explicitly idiot-proofed: meaning that if you do your homework and a little bit of extra maintenance, you don't suffer any drawbacks at all and get all the positives.

For what it's worth on the street, (well maintained) loose ball bottom brackets have less bearing drag and therefore spin easier than sealed bearing bottom brackets. Even hardcore trackies, though, realize that if they're worried about bearing drag, they're probably so fast at this point, they can have someone build a custom bottom bracket just for them.

With regards to the paint jobs of NJS bikes, they are definitely not winter-worthy. The paint is generally painfully thin, as nice as it may look. (I echo the opinion of some others in that I prefer the more understated look of single-color paint and small builder decals.)

For winter, it would probably be better to have something with fenders, clearance for wider tires, and a heavy powdercoat finish.