I Just Went into my slime farm and AFK'd for like 10 minutes normally i would have like 1-2 big slimes and 2-3 medium slimes, but after the 1.2.3 im getting 4-5 big slimes i might be wrong but to me they seem to have increased
Don't think it has anything to do with 1.2.3... I'm still running 12w06a and that happens to me sometimes as well... Depending on your setup (limited ceiling height for example), you could have been getting more bigger slimes that broke down to the medium slimes but you didn't notice before. It could also be that mobs elsewhere despawned/died which gave the slimes more chance to spawn and so you got the "extras"... As I've been lighting up my caves I've definitely been seeing more slimes spawn.
Slime Spawn Rates Increased