I've been running this servo in my 2WD offroad since last April:
http://www.hobbyking.com/hobbyking/s...g_0_06Sec.html
It was the fastest cheap one I could find. 0.06sec. Doesnt have the greatest torque but I find it fine in my 2WD. Like I said, I've been running it since April, 2 meetings a month minimum, probably about 3-4 in the summer months. No issues.
If/when it breaks, I'll probably buy another one.