It looks, when I checked quickly, that the most significant (to you) changes are:
Different handling of RTL "am I there?" check, so that it uses the WP radius, rather than a static 4m circle to determine if the AC has missed the WP.
Changed Loiter PIDs
Loiter_P 1.0 -> .5
Loiter_I 0.01 -> 0.0
Nav_P 2.0 -> 4.0
Nav_I 0.10 -> 0.25
Nav_IMAX 16 -> 20
There was also a move of an ADC filter outside of HIL, so it would not take place in HIL
There were other changes on the 2nd and 3rd, to add a limiter to the ramp up of speed for waypoints, a second PI loop for alt hold, increased gains for the jdrones frame, and removed some test code to help for 1280 space issues. But I this I think was maybe compiled into 2.0.46 before the firmware number was incremented, so I guess you can consider that 2.0.46, as I think it was pushed into a refresh of 2.0.46.
Here is the changelog
commit 2ceba2f12fb0d280420262385daefad63a1e24bdAuthor: Michael Oborne <XXXXXXXX@gmail.com>Date: Fri Oct 7 11:58:29 2011 +0800
commit 924d3d9cf2cb1f82d8840cf49a61b201566120d2Author: Jason Short <XXXXXXXX@gmail.com>Date: Thu Oct 6 17:42:09 2011 -0700
Better Loiter PIDs Fixed RTL overshoot bug
commit af59ae9e2f956a560f4ce05476674167d1c47f50Author: James Goppert <XXXXXXXXXXXXX@gmail.com>Date: Thu Oct 6 19:17:49 2011 -0400
Updated APO, HIL working well, live mode ready to test
commit 26a64775753d0711b696aa10a55849bc5838a9d8Author: Michael Oborne <XXXXXXXX@hotmail.com>Date: Fri Oct 7 06:45:54 2011 +0800
add missing file
commit 64e309391958f304520453cf791a8d5e694303eeAuthor: Michael Oborne <XXXXXXXX@hotmail.com>Date: Fri Oct 7 06:41:17 2011 +0800
APM Planner 1.0.79 - add Russian (thanks YureZzZ) cleanup add new ac2 pids
commit 1b0fe76ef068a25b059dd4a524d097e247e727f8Author: James Goppert <XXXXXXXXXXXXX@gmail.com>Date: Thu Oct 6 12:00:45 2011 -0400
Reducing copy ctor calls in apo.
commit 1b971c67cd01eccca3eb8f9820a23210ebc20e58Author: Michael Oborne <XXXXXXXX@hotmail.com>Date: Thu Oct 6 07:43:16 2011 +0800
APM Planner fix resedit for other languages
commit 60dc36bd0daa974218fe0deb8cfdfbcafb2b12c0Author: Michael Oborne <XXXXXXXX@hotmail.com>Date: Tue Oct 4 19:19:25 2011 +0800
APM Planner 1.0.77 misc fix's
There are also changes to libraries, but I did not see anything that you would likely be interested, with a quick check.