I can't stress how much I love this ability. It has not only won a few arena matches for my team, but has also saved me in PVE countless times. Some cheat death times:
Heroic Arcatraz: I lagged out slightly during the Dalliah fight and couldn't run out in time. Her whirlwind crit me for an absurd amount, killing me. Cheat Death kept me alive so I could continue DPS'n and more importantly kicking.
Heroic Mechanar: Tank died on the lolfirelady when she was at 2%. I was the last person left standing, and thanks to evasion, cloak, step, dirty deeds and cheat death I killed her all by myself that last 2%.
Arena: On the most OP team possible (pally/war) I had just killed the pally and the war had just killed the priest. I still had a good amount of CDs up but you know how ridiculously strong warriors are at single combat. Each hit I was taking was knocking off a good fourth of my HP (as this guy was apparently geared too). My blind finally came back up when the warrior execute crit me for 5k and was absorbed by cheat death (keep in mind, that's half of my total HP). Not a second later I blinded him. I got a restealth and was able to win the fight with a fresh stunlock. I would have died to the execute otherwise.
Those are just a few of the many, many times this ability has saved my ***. It's given me back the ability I always loved about the rogue class: I die on my own terms in PVE and have more tricks up my sleeve than Gambit in PVP. I love it.