How does Siverlight 5 with P/Invoke compare to XBAP with FullTrust?

Question

I'm considering XBAP with full trust, but just heard about SL5's ability to P/Invoke. This is quite exciting because XBAP deployments are very difficult considering it only really works with IE, works sometimes with Firefox, and never with chrome.

Does anyone have details on this feature, and its cross browser support (on an x86 machine of course)