With regards to rust, I use either Birchwood-Casey Sheath or Fluid Film on all of my knives, especially the AUS series ones that have been bead blasted or stonewashed like the Spartan. These rust prevetatives don't need to be reapplied very often at all, but I typically reapply once a month or so if I've been using the knife. You can get a 2.5 ounce can of Fluid Film for about $5, and that'll last you a damn long time, as you only need a spot's worth of it on a rag once a month or so.
The edge of the grivory along the blade channel of the grip, where the meat of your fingers grip, is very sharp from the factory. I used a Buck 110 to shave off the whole edge on both sides, and finished it off with a very fine jewelers file. Sandpaper would work fine as well.
The action needed a little lubrication, and the pivot required a very slight adjustment, no big deal.
I tied a doubled up piece of leather boot lace to the lanyard hole, knotted at the hole and double knotted at 1" as a fob, to make deployment from the pocket easier. I also installed the included left side pocket clip and left the right side one on, so that I can switch pockets easily. If anything, having both pocket clips on improves the(already excellent) grip, as it gives my pinky a nice spot to rest.
I've been carrying the Spartan every day for about a month in heavy jeans, and it rides very comfortably in the pocket, so that I don't even notice it. I've had smaller knives that felt bulkier in the pocket, like the large CRKT M16 or the all-stainless Endura
The only other thing is that unlike other waved folders, the thumb plate works better when drawn all the way to the edge of the pocket, so the plate straddles the crease. Drawing it out and to the side like works with an Endura or Emerson doesn't work so well. Once you get the hang of it, opening it wave-style is easy and 100% effective.
I've been very happy with it, it is a very comfortable, effective large EDC knife, and I'd bet that it would do fine as a defense blade if you so chose.