I have the TK1 in the SGPS (3G) and it is a remarkable blade! It holds an edge seemingly forever. The trick, like with any steel, is to not let it get dull. I've tried to abuse it with camp chores but it holds an edge very very well. Normally don't need to sharpen it. Edge lasts much longer than any of my VG10s (more like my CPM 10V).
Stropping restores the edge really quick. When it gets dull I sharpen with a diamond steel first followed by fine sand paper grits on the mouse (I take it up to to 2000 grit then strop). Takes less than 30 minutes for me when it's really dull. Fallkniven makes a nice little ceramic/diamond dual grit pocket hone that's ideal for this steel.
If you have a choice and can afford it, get the SGPS. It's a great HARD use knife steel.
NJ