I just got a notification that the official Microsoft Facebook app for Windows Phone 7 has been updated to version 1.5 (current release is 1.4).
I checked the official Facebook for Windows Phone 7 Facebook page to see if any info was posted concerning this update and what it fixes but the last update is from 9 days ago.
Looking back on the apps wall it seems that this may be a login fix that was mentioned on 07 April 2011:
If you can’t login (since today), please uninstall and reinstall the app.
We changed a server-side setting today from 9 AM PST to 11 AM PST. If you logged in during this time, you might have a corrupt token. We will roll out a fix for this asap, but that takes a day or two, the workaround for now is to uninstall and reinstall the app.
Looking back it seems version 1.4 was to fix a Messages error that was crashing the app so it makes sense that version 1.5 is to fix the issue quoted above.
I would also take it that this also means that version 1.5 is not the major update they have reportedly been working on. Maybe that will be version 2.0 down the road?
Check out the program listing at wp7applist – http://wp7applist.com/app/1738.