I changed mine today for the first time on my new 06 double cab at 700. Nothing special about that mileage, just that it was a nice warm Fall day and I had the afternoon off. Put in Mobil 1 5W30. I will change it again at 5000, and then thereafter every 5000.
I actually think that if you're going to change your oil every 5000 as Toyota recommends, then you probably don't need synthetic, the dino should be just fine. However, I live in Maine and we get some seriously cold winter weather.
The other reason I use synthetic is that when I took the valve cover off my old 1986 Jetta when it had 145,000 miles on synthetic--- it looked like a TV commercial--- everything shining like brand new stainless--no gunk, nothing brown and black, just perfect.
Seems like cheap insurance to me to go with synthetic if you plan to keep your vehicle a long time. If you're someone who trades every four or five years, I'd say don't waste your money on synthetic.