Stealth play is amazing. Stealth is my primary attack skill. I sneak up, or try to, on every foe. Your speed matters. Your armor matters. Enemy facing matters. Shadows matter. Line of sight matters. Backstabs can be devastating.
I use dual daggers. I sneak up on everything. You fail a fair amount but even with a sneak in the 20s, moving slow, underground, you can sneak up on stuff. Time it with guard movement. Use obstacles go move up. Lose archers circling a pillar chasing you then falling back go the next pillar, then moving up and backstabbing them as they look for you on the wrong pillar.
Once stealth gets in the 50s, it gets so fun. You can sneak into and out of some hairy situations, and deal massive silent backstabs.
At skill 70, you are Batman. Or Evil Batman. You can sneak at top speed and be as stealthy as you are standing still. I was doing stuff like creeping into mess-halls where a guy was eating, killing him, and jumping out of the room before the 3 sentries could react, and losing them in the cave tunnel and looping around and picking ghem off. Killing 3 guys standing in line watching a 4th guy forging a weapon, then killing him, with nobody aggroing or knowing I was there. Rising up out of the water under a watdrfall in a bandit cave like flippin RAMBO covered in mud, killing the bandit leader who was 3 feet away and *looking right at me* with a massive x15 dagger strike.
At skill 100, its just insane. Sure, one slip and you could have a nasty fight, but as long as you dont make any mistakes, even the most sensitive and deadly foes can be snuck up on. I sneak up on tigers, dragons, heck even dwarven machines with infravision.

I cleared a series of tunnels with about 20 or more insect demons in it, and not one ever saw me. Not even the massive boss and her 2 lieutenants. It was dicey, but I dropped behind a LT, let momma boss (who was 5 feet away) look left. I backstab and slip into the water. My eye never shows me as unhidden but she sees the body and explores. I slip in and one shot the other lieutenant. Then her. Not one of,them aggroed on me the whole time. But they could have. Some foes will take all your skill to sneak up on, even fully perked. But you can do it if *you* do it right.
This stealth system is so fun. You will go from cool, to scary, to epic. But there is always that risk, that window of fail you can always fall through if you blow it.
Good times!