<p>For reference, this would be for Visual Studio 2008 with a fair amount of WinForms working with the VS Designer.</p>

<p>Given the same price bracket, would there be certain specs you look for in a development rig vs what one would get for a gaming machine?</p>

<p>Edit: The reason I ask is on my laptop that I can run low-mid end games decently on, there's still a fair amount of time redrawing when switching between apps sometimes.(I keep about 20 tabs open average on  a browser and have like 10-15 apps open at a time), and working with the VS designer on things like a TableLayoutPanel takes up to 10-15 seconds for changes and so forth. I'd like a really smooth experience.</p>

Any new video card you could buy today would be more than adequate for non-3D software development. In fact whatever integrated video came with your system is fine. The only exception would be for multiple monitor support, in that case you would need to get an extra $50 video card since most (all?) motherboards only have a single monitor output.
Edit: in response to the edit, the lag you're describing sounds like your machine is out of RAM and is swapping to disk, rather than you being video card limited. You'll want at least 2-3GB of ram in your system if you're running vs2008 plus 20 other applications. That's about the max. you can install if you're running a 32-bit operating system. If you want more than that you'll need to go to a 64-bit OS and you'll need to make sure all your hardware has 64-bit drivers. Also very few laptops out there support more than 4GB of RAM.