The F2 zooms are pricey - but they are Pro grade glass and thats going to cost some serious $$$ no matter which brand you buy. If you wait and get say the E510 and say the 50-200f2.8-3.5 or 12-60 f2.8-4 IS will give you that extra stop or possibly two so you could in effect have an 50-200 f2 - 2.8.
Here's a shot taken with my E1 and 14-54ZD on Friday, at ISO 400 F5.6 @ 1/2s handheld at 44mm (88mm equiv. 35mm). My third attempt at the shot, the first was a landscape.
You might also want to take a look at the 50mm (equivalent to 100mm) f2 macro - its basically like having 2-3 lenses (1) a macro lens; (2) a portrait lens and (3) a low-light lens. here's a review of the 50mmF2: