Remember, rested and the Midsummer buff only affect experience gained from killing things. Heirlooms boost both killing and quests.Tested on level 42 mobs for consistency.
Lvl 48 Rested vs Unrested
- 2 Heirlooms: 392/196
- 2 Heirlooms, Midsummer Buff: 424/212
- 1 Heirloom: 358/179
- 1 Heirloom, Midsummer Buff: 392/196
- Midsummer Buff: 358/179
- Nothing: 326/163
Results: Rested doubles the effects of all stacked experience buffs when killing mobs.
Implications for Leveling: I strongly suggest only leveling when rested to get the maximum impact for your time. Rested bonus with no other boosts (326) is still better than the Midsummer bonus with heirlooms (212).
In Cataclysm, I plan to have all my alts resting and then try to use the rested every time it caps on one of them. This is how my husband's best friend leveled his 7 alts -- rotating through them to get the maximum out of their rested states.
Even without heirlooms on my characters, I'll be more efficient playing un-heirloomed and rested (326) than playing long hours with 2 heirlooms unrested (196).