How important do you think it is for a laptop to have a dedicated video card?

I've never had one with a dedicated video card but I don't see this as a biggie. I can't imagine that you could upgrade the video card in a laptop and, to me, that seems the only reason to have a separate card. Incidentally, that's the reason my son's next gaming system will be a desktop/tower rather than a laptop.

If you want to play 3d games or develop with Cuda/OpenCL, very. For browsing the web and 'normal' development, not so much.

Neither my MBP and XPS have one, both are lightweight and quiet, and both cope fine with a big external monitor.

Also, if you plan on running Linux on your laptop, drivers become an issue. Especially if your machine supports switching between onboard and GPU modes.

It depends is the correct answer I think. For systems with Intel processors, there is a built-in Intel GPU that these days is pretty good from the performance perspective. If you don't need the highest performance graphics (top-end gaming, video processing, etc) then a dedicated GPU such as an nVidia card is overkill.