Slow wakeup from sleep with 10.7.2
This might be because your system enters "standby mode", where it actually saves all your data to disk and turns off. When you start up, it restores everything. 30 seconds is NOT normal though. However, a fix that you might want to consider is to disable this functionality:

sudo pmset -a standby 0


The result will be that your MBA should no longer enter "standby mode" anymore and sleep like any other MacBook. It will consume battery power while sleeping, but should wake up instantly.