Previously, rupture was a static damage finishing move that offered the same DPS no matter how many combo points were saved up -- additional combo points only extended the duration of rupture. The prevalent strategy was to gauge how many seconds left your target had to live, and to only use enough combo points to match it. However, rupture was overhauled to improve its scalability and make it a more attractive ability for end-game use.
Rupture now increases damage and duration per combo point used. It also factors in a percentage of your total attack power as bonus damage that is spread out over the duration of your rupture. The bonus damage from your attack power scales based on the number of combo points on the target.
Save this for longer fights, or fights against highly-armored opponents.
Be careful of using any DoT-type attacks, as it commits you to the fight in that many Crowd Control abilities will be broken by the damage it causes.
As of patch 2.4, skeletal and non-corporeal undead (such as wraiths), elementals, and mechanical creatures are now susceptible to bleed effects.
Works well against other rogues who may use vanish to escape, since any damage removes stealth.
The 5 piece bonus of the Madcap's Outfit armor set reduces the energy cost of Rupture by 5.
Patch 3.3.3 (2010-03-23): The damage-over-time component of this ability can now produce critical strikes.