Laptops are no different from cameras in that you get what you pay for. And, more often than not, a compromise must be reached between budget, weight, portability (size) and power.
There are some great ultrabooks coming out soon, but, just as you did with your camera and lenses, you should consider how you will grow into it.
File sizes are only likely to get bigger, will you be doing more video in 1 or 2 years etc etc.
As has been already mentioned the CPU and GPU is very important when choosing a compauter especially if you are doing stuff like rendering HD video etc.