I assume Microsoft will follow Apple's approach of allowing multitasking with approved background processes instead of full apps.
My multitasking experience on iOS is even better than Android, thanks to some clever features of the OS's media player and also the work Apple did to comprehensively determine which app processes should be allowed to multitask. I can background both a video call and turn by turn navigation (MapQuest4Mobile fills the gap here fairly well) while I'm off browsing the web, and other standard multitasking convenience features, like downloading apps or store content in the background, is supported. You can even use Shazam to identify music playing through the iPod/media player in the background.
My favorite multitasking feature that I believe only iOS actually does is the ability to background any video, including YouTube videos, into the media player. YouTube is the largest source of custom mixes and covers of songs (as well as having the original songs there too many times), so getting music on demand from YouTube while I work elsewhere on the phone, or simply leave the screen off to save battery, is very nice. Audio lectures and audio books are also nice to run this way.
I don't get many app/content reloads when jumping around between games, camera, browser, phone, and messaging on iOS, and I get the added efficiency of the OS never running processes like full UI threads for background apps.
Then again, other than the lack of being able to run the audio from YouTube videos while elsewhere on the phone, my Galaxy Nexus's full multitasking hasn't brought me any apparent issues with processing lag or battery drain, so I've been very impressed with Google's latest so far, as well.