There's a few bits about Stealth and sneaking around that need to be reworked a bit to make the skill a bit more functional. As it stand right now, it's full potential is held back and loses value at higher skill ratings.
1. Hostile actions shouldn't immediately put you out of stealth mode. As it stands any hostile action puts you immediately out of stealth mode, even for things that shouldn't. If I have a high stealth, stealthily open a door, and pitch a grenade into a room of unsuspecting people... They shouldn't immediately know where I am at. After the effects of the grenade, they should start immediately looking to try to find where it come from. Depending on the attack and maybe some perception checks, they should get a hint as to where the attack came. This would allow them to go into a search mode to find you and give them very high bonuses to their ability to detect you since they are on high alert. And further hostile actions towards them will grant them even more bonuses in finding you. This would effectively put most low level, low stealth skill characters out of stealth. But for those who dedicate skill points to Stealth, they'd get the benefit of being able to do a few attacks without immediately being detected.
2. Instead of the binary "Hidden/Not Hidden" mechanic, there needs to be degrees of stealth. The awareness "Eye" icons should indicate the tier of penalty being applied to all actions when in stealth: Green = No Penalty, Yellow = Minor Penalty, Orange = Moderate Penalty, and Red = Major Penalty. This creates a more "Press Your Luck" mechanic that puts player more on the edge. It allows more opportunity for various stealth actions with the balance that you can be technically detected at any time by a bad roll.
3. Stealth awareness "Eye" levels need a drain down. As it stands right now, Stealth awareness is a cumulative mechanic. If the changes above are made, a drain down should be added. This would account for when NPCs move away from the player character, NPCs get distracted, or, depending on the player's feats, reputation, or high stealth skill, NPC's start to not pay the player that much attention.
4. The Stealth Mode cooldown should be removed. What's the problem with trying to hide whenever you can?