Tiny is my favourite hero. Flexible and still packing some insane DPS, he can pretty much take on any hero 1 on 1 thanks to low CD abilities.
Brewmaster is another hero I really like to use. I'm still trying to get the hang of him, but his ulti is whoa.
acare84: You can play the game with bots and learn. :)
The bots are still shit. I hope they improve on the bots that are on your team. That, or let smaller teams receive more money per player - hopefully this will be the case in the final version. The bots don't do anything except feed the enemy.
I need to start playing on pubs soon, but I'm hesitant. I play games to unwind, and I've been hearing so much about pub horror stories. I once played DOTA1 on a pub server, and boy. I sure wished someone had invented a device to let me punch another person on the Internet.