I wish Microsoft would do this here...

[Anakha56]

http://www.gsmarena.com/microsoft_exchanges_iphone_4_4s_galaxy_s2_for_lumia_1020_1520-news-7752.php

Microsoft offers a Lumia 1020/1520 for your iPhone 4/4s, Galaxy S2

Just two days ago Microsoft announced a new trade-in deal for the US and Canada, which can give you up to $250 of store credit if you give up on your old smartphone or tablet. Today Microsoft has extended this deal with a special offer.
If you opt to return your old Apple iPhone 4, iPhone 4S or Samsung Galaxy S II, you can have a Lumia 1020 or Lumia 1520 for free. Your old phone just needs to be working, with no missing parts or pieces. The deal expires on March 2, or until supplies last.

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Follow the link for further reading. I wont actively go out and get a MS phone but with a offer like this I could be tempted...

 

[The_Ogre]

Qualifying 2-year (new or upgrade) contract required.

That alone, doesn't make it as attractive as it seems at first glance...