This section of the forum looks like its in need of a little more discussion!
So i've decided to do a short, but hopefully informative write-up of how i find success as the UB.
the first thing to consider, is the UB's general stats.. you'll notice he has a higher speed than the other demigods - but sacrifices health - at least in the early stages.
So to start with, i reccomend purchasing the 1k boots that give +10% speed, should make it a lot easier to keep ontop of whichever DG you are trying to apply pressure to, and will further increase the UB's selling point - Speed!
Once you've played a few tournaments you should have enough Favour points to unlock the assasin upgrade that gives a bonus to weapon strength, with a 15% chance to increase your attakc rate by 50% for 5 seconds..
this is an extremely powerful item when employed by the UB. stacking up some other + attack rate items.. allows the 50% attack speed boost to be triggered a lot more than youd think, this combined with high Bestial Rage can be lethal - very fast.
My General skill progression is to level bestial rage and grab the first rank of the venom spit ASAP, destroying the creeps as fast as you can untill you hit level 5, and unlock post mortem - with luck/efficient play this can be achieved suprisingly fast. at this point its simply a case of farming those creeps, whilst venom spitting any DG that comes near.
I find that once i am relatively set up with semi decent equipment, at around level 7-8, it is possible to teleport to an enemy DG, and completely obliterate it in seconds if the 50% boost triggers, if it does not, then you will severely maim the enemy, but be forced to withdraw in most cases. - Don't forget to apply Venom spit at the start of the combo.. your physical attacks when sped up, mixed with the venom make for some jaw dropping Ouch factor - enough to make my mate rage-quit quite a few times 
Haven't had much sleep tonight, been up playing some lan fights with a couple of mates - so if i've missed something out, or if something doesn't make sense, please tell me and ill add more detail!
Summary:
Play to UB's Strengths, get +attack speed and + speed items
Live to fight again, if its gone tits up, RUN - use that speed - dont give the enemy that gold boost
Suprise is key.. make use of teleports, or warps, distractions.. anything you can to get a suprise strike, if all goes well you can disable an enemy in under 5 seconds.
Don't bother trying to do an all out 1v1 with the above setup, at least not untill you have leveled up a bit.
soften up a group of enemies by Spitting at the weakest enemy, and then run, and return and spit, be annoying, frustrate them, wait for one to make a mistake by overextending - then grab the kill.
----------------
That should do for now, if you'd like more detail on items/skills @ which levels etc, go ahead and bring it up, i'll make a note of what its all called next time i tab back into the game 