I'm re-spinning a board with the CC2420 and am thinking about replacing it with the newer CC2520 as long as it does not require a significant amount of software work (trying to keep this a small project).  The CC2520's datasheeet mentions a 'CC2420 Interface Compatibility Mode', but does not go into much detail about this feature.  Has anyone ported code interfacing with a CC2420 to a CC2520?  If so, was it relatively painless?  I noticed the CC2520 errata mentions a glitch on the FIFOP GPIO, are there any other gotchas to know about in porting code from the older to the newer device?  What I'm basically looking to know is, if I re-spin the board with the CC2520 and tell the firmware department it should be a simple and straightforward code port to the new part using the 'CC2420 Interface Compatibility Mode', will I be telling the truth?

Also, for anyone at TI with such knowledge, do you think there is any concern with sticking with the CC2420 (if decided to go that route) for long term manufacturability?  With the arrival of the CC2520, are there any plans to phase out the CC2420 in the near future?