The shared video memory would be an issue if the server is hosting video clips, etc I guess but otherwise if mostly doing processing perhaps it is fine. Hyperthreading allows the processor to run a bit faster while multitasking so this may also be beneficial on a server.
A Pentium M cpu is designed for a notebook to have the most efficiency with wi-fi usage and battery life (and to generate less heat) versus a Pentium 4M cpu. A server is always going to be plugged in and you want it to run at full processing power if it is hooked up to the the web or a network. A Pentium M cpu throttles down to a lower cpu mhz speed to conserve power and only ramps up to full speed when needed.
I have no idea why you would want to use a notebook primarily as a server --- you would be better off with a desktop. But at any rate, I would not recommend a Pentium M Centrino for your purpose but I do recommend it for most notebook users (except extreme gamers and true desktop replacement users who want a 17" LCD and don't care about thickness, weight, and heat).
Note that many desktops have 4 memory slots and you can upgrade from shared video memory to dedicated by adding a video card to an open slot at anytime. A Notebook only has 2 memory slots and the video memory is not upgradeable (at least for the normal user and also not for an affordable price after the sale either).
I was looking to buy the new Toshiba A75-S229 Pentium