Questions about bringing AT&T Lumia 920 to Straight Talk

I'd like some advice from someone who's been through the process.

Currently I'm on Virgin Mobile. Tomorrow I intend to preorder the Lumia 920 from AT&T and port my number to them. After a month or two, I intend to switch over to Straight Talk, paying the ETF. No big deal. Long-term savings, etc. And I don't need LTE (coming from Sprint's network on Virgin, AT&T's 3G will make me very happy).

So, I assume I buy a microSIM from, and when I active the SIM on their website, I can again port my number to their service. Then I have to tinker with APN settings and what-not to get data, MMS, etc all working properly.

Are there any holes in this plan? Have any of you successfully gone through this with Windows Phones locked to AT&T/while you were still on contract? Some googling showed me some people had issues getting MMS and/or data to work even after tinkering with APN settings.