As you know, custom ROMs require custom recoveries and official builds require their respective official stock recoveries; if your Streak doesn't have the correct recovery image installed, you'll see an ugly side of its personality when you try to flash the "wrong" ROM. The device can become uncooperative, stubborn, frustrating, and downright unpleasant when you try to mix incompatible ROMs and recoveries, so it's best to make sure you always have the right combination.
UKSheep released version 0.4 of Multi Recovery Flasher over the Easter weekend, and it now includes the recovery image needed for last week's official Android 2.2.2 (version 15609, build 351) update for unlocked Streaks. So now anyone currently running some combination of, say, StreakDroid and ClockworkMod/StreakMod can check out the latest Dell build without having to locate the proper recovery image first.[xda-developers]