I have this sterling silver wire custom made for me with rounded edges (lengthwise), although in this wire (which is thinner than the 5mm x 1.5mm wire) the rounded edges are less noticeable. When this wire is made into a bangle, the rounded edges give the bracelet a more finished look. This wire is dead soft, which works well with stamping, but it is quite thick so it naturally has a bit of hardness. The stamping and shaping harden it enough to stay stiff in a nice cuff or bangle shape.
I use this wire to make cuffs (no clasp) with stamping on it, or wire wrapped beads on it... or both! Make sure you have a good file that will smooth out the cuff ends. I like the beefy ones that I carry because they remove a lot of material in a small amount of time, and then I just work it a bit with fine grit sandpaper (which can be found at a hardware store).
Lisa Niven Kelly uses flat wire in her Say It On Your Wrist, Stamped Cuff