I just rooted mine today and had no problems. I used this one... http://forum.xda-developers.com/showthread.php?t=2290798
As for the download mode, I held the Down Volume, Home and then when those 2 were pressed I held the power button. It took a few seconds and then went into download mode.
Also when I flashed the first time it turned on the "show pointer option" from Dev Tools which scared me at first because I thought I broke something.
Everything is running fine now and works great! Good Luck!