I just got my MBP 13" yesterday and installed Mushkin's DDR3 1066Mhz RAMs into it. Working fine so far, and Switch themselves recommended me Mushkin. According to them, they used to install Kingston but sometimes the MB cannot detect.. but after they changed to Mushkin, no problems so far.. not sure la..

I just switched to Mac myself and was speculating what sorta RAMS I should have gotten.. I personally was using Corsair RAMS on my Win laptop and desktop but I when I asked Switch regarding Corsair RAMS, they weren't so sure about the compatibility. They said Crucial is ok, Mushkin are the ones they use right now and Kingston was what they used previously.

I believe you should get 2 sticks for now, 1 because it would be cheaper and you can bargain, 2nd because Snow Leopard is coming out soon which is 64-bit and can support all 4gb of your RAMS.