It provides a 15% damage bonus for the 5 seconds after you decloak.
That plus the fact that you can use it to get to optimal range for cannons (5km), optimal position on your target undetected and have all your buffs activated before decloaking, means you can get a respectable bit extra out of your "Alpha-Strike" with it.
It lets you pick where and how a fight begins. Particularly in PVE where few enemies heal or boost their defense, you can simply appear on their 6 at point blank, alpha strike them, and never have to deal with whatever annoying power they'd use if you were in their front arc. Or appear on a side and neutralize those pesky torpedo salvoes. Or coast by entirely on the missions that don't require Kill Everything, if you don't want to waste the time. For added fun, toss on a tractor beam and control the fight completely for the first 10 seconds, and ensure it won't last longer than that. Cloaks are FUN.
I'm going to try using sensor masking to sneak up on those VA dil reward objectives in Gorn Minefield. It's a pain to deal with 30 odd Gorn frigates and half a dozen cruisers if I happen to need to retrieve a rare mineral sample solo.