I, personally, would never attempt to use a laptop for design. I am not trying to push our computers by saying this, it is just something that I hear a lot.
Laptops do not have near the performance of a desktop, even the custom RAID laptops.
We build custom laptops too, but for design, it is a bad road to travel.
Vista works well with Photoshop and only the newest version of Flexi supports Vista (8.5?).
What about a MAC book pro? (as far as designing with photoshop and illy)