To test your theory, I reinstalled the update, went offline, and timed some basic actions:

V21.2.2.415 V21.2.1.379 Diff.
Start Family Tree Maker & open tree 0:17 0:20 -0:03
Click on current person from Plan 0:41 0:03 +0:38
Click from Family to Person tab 0:04 0:01 +0:03
Click from Person to Family tab 0:41 0:01 +0:40
Click from Places to Family tab 0:41 0:01 +0:40
Click from Family to Media 0:04 0:05 -0:01
Click from Media to Family tab 0:41 0:01 +0:40
Click from Sources to Family 0:41 0:01 +0:40
Click from any tab to Person 0:01 0:01 0:00
Run Extended Family Chart 2:09 1:29 +0:40
Export from Chart to GEDCOM 2:35 2:37 -0:02
Export to FTM for Mac 2 15:33 17:14 -1:41
Quit FTM without auto-backup 1:07 1:30 -0:23

All times are in min:sec.

Obviously I was not able to test the sync function in offline mode, but I'm willing to concede that some of the sync errors may be due to Ancestry's servers being swamped by people viewing the 1940 census. In addition, most crashes I experienced seemed to occur during or after a sync; I did not experience any crashes with the update during my tests, while the previous version crashed while running the Extended Family Chart and exporting a FTM for Mac 2 file.

Aside from exporting the FTM for Mac 2 file and quitting, the update was significantly slower whenever the Family tab was clicked or running the Extended Family Chart. Clearly there's an issue with the Family tab that has nothing to do with Ancestry's servers being swamped; it should not take 41 seconds to load, when the Person tab takes only a second. I have provided these results to Ancestry Support and will report in this message thread their response.

(Note: I timed these actions on a MacBook Pro with a 2.5 GHz Intel Core 2 Duo and 4 GB of RAM running OS X Lion. My FTM file has 22, 342 people.)