Hey personally I've been using a method from a website which I've forgotten now. Basically it's taking those thin plastic files or folders or dividers and cutting them up and using contact cement/adhesive to stick them on. I've experimented with tiles before, but the cut-up-files are seriously the best way of replacing that I've come across so far. Unfortunately I can't talk about the cubesmith stuff because I've never used it before.
Tiles:
Pros: Doesn't peel.
Cons: Thick, heavy, chips so you might need to replace them, feels funny, makes the cube feel bigger.
Stickers:
Pros: Thin, light, alright grip.
Cons: Peels, needs constant replacing.
Files with contact cement:
Pros: Can be as thin as stickers if you find the right sort of files, light, NEVER peels, NEVER needs replacement, can choose your own colours.
Cons: Takes a bit of time and effort to replace all the stickers, might not be able to find said colours.
So, what I'm saying is to use the files with contact cement. The contact cement/adhesive is important, because otherwise they kind of just fall off. But as I mentioned, I've never used the Cubesmith stickers, and so they might turn out to be superb stickers which never peels and last forever. Anyway, from what I heard it's probably worth a try for me to check them out.