They slowed the combat pace way down, and removed a lot of the tactical positions that the old 3v3 was known for.
This included the wall between top and bottom lane that could easily be flashed through (fighting for bush control isn't as important, and promotes defensive gameplay).
They also removed both white and green buffs, which were extremely important to the top lane who also had the role of jungling (Which is no longer the case, there is now an optional dedicated jungler in 3v3, once again promoting defensive gameplay).
They replaced the well positioned dragon with a not so well positioned, yet awesome spider that is much less tactical, since you can only kill it much later in the game (Once again... More defensive gameplay).
They added 2 capture points WHICH IS A TERRIBLE IDEA, making 3v3 feel like a side-game (such as dominion), rather than a smaller alternative to vanilla 5v5.
Overall I feel that the bottom lane was an improvement, especially in the removal of that trollish bottom bush that people suicided into.
I would give the current 3v3 map a 6/10 if it was a side game, but they threw away a perfect map for an average, yet boring gameplay experience.