1.8GHz Core2Duo? That’s the low end of that line… only thought they started at around 2GHz.

Would you believe, someone asked the exact some question somewhere else over 2 years ago? The upshot is that a 2.8Ghz P4 can, depending on what test you run, come close to a 1.8GHz Core2Duo, but the newer chip’s still got it beat in general. Better at multitasking, it’ll run cooler and with lower power consumption, and it’s going to be faster (2 cores at 1.8 can beat the crap out of a single core at 2.8, so long as you’re using both cores)

That, and double the amount of RAM, it’s a better machine. No question. So if you want an upgrade and you can afford it, I’d say go for it; $350 is a better price than you’re going to get anywhere else.