Everything will work the same as always. Older games that need a patch will still work with whatever patch they require. Older games do not need TB specific patches to work.
The Battlefield 3 fix will still work even if you use TB custom firmware. Same as Uncharted 3, Alice Madness, etc.
You actually do lose one feature with True Blue firmware. You will not be able to play backups of PS1 games. I think that is the only feature I lost when switching.
Please always assume I am joking, because I always am. Except for right now..in this sig...I am serious. Seriously!
320gb Xbox 360 RGH
320gb PS3 slim TB w/3TB external
80gb B/C PS3
PS Vita 3G/WiFi