I really like the Escalation Die; it speeds the game up and frankly if a combat has gone 7 rounds, one of three things has happened:
1. I've over-built the encounter (likely too defensive) and the combat is dragging on. +6 to attack rolls makes sure it ends quicker.
2. The party is in dire straights, having been beaten on for 6 rounds already. +6 to attack rolls has a heroic comeback feel.
3. The fight is essentially over, and they are just mopping up. +6 to attack rolls ends it that much faster.
I also like that encounter powers aren't automatically recharged; players don't just blow them right away, because they might have to go without them for the next battle if they miss their recharge. In conjunction with the Escalation Die, some powers (cyclic spells, barbarian raging, etc) are free to use after the escalation die gets to a certain point.