http://temp.tmalliance.com/?num=1305239991Heres a comparison on damage numbers for car's special between two versions! Credit goes to Kilrahi and Stitches.
Yes besides the obvious network play, 4 players being bumped to 8, there were several new modes... Manhunt (one player is "hunted" while everyone tries to kill them, whoever does will become new person being hunted). Collector - where you have to stockpile these triangles and get the most. Last Man Standing (Set amount of lives), and standard deathmatch. You could play any map with however many players you wanted, unlike TMB. 8 players on dogpound is possible.
On top of those modes there were various scoring methods: Kills Only, Net Kills (Kills minus deaths), Net Damage (Damage Done over Damage Received), Damage Only, and Carnage (Damage Done + Kills).
Add to that there were optional relic pickups, these were like a bonus modifier that you could carry (only one at a time), one might be parasite - a percent of damage done is tranferred to health, or Blitzkrieg - increases rate of fire. When you died carrying a relic, it is dropped, and you could drop any relic at any time on command.
Certain cars were changed as well from TMB to TMBO. Not just in how much armor they had or how much damage their special weapons did, which is shown in that link I posted earlier. Mr Grimm's scythe special now has a slight homing ability. Warthog's special now fires fireballs as well as Flame jetstream. Outlaw's special (his red laser removed completely -now only have to tap button to fire blue missiles), Yellowjacket's spikes, Shadow's secondary special, and Brimstone's special now have their special's homing ability increased triple-fold. Crazy 8's tazer and Axel's shockwave's radius have been increased substantially. All these changes were likely made due in part to compensating for lag. While increasing the homing ability on some specials was absolutely neccesary, they are still very much dodgeable.