I should also point out that graphic card drivers are often an issue with OpenGL applications (like a large scene in DS).  But it depends on the type of stuttering you are seeing, is it in the viewport or the whole computer?  Only while rendering or only when working with the scene?.  I think most people would be surprised at how often open GL stalls end up being driver issues.  To be fair it isn't always the driver writers fault.  Usually it's the app doing something strange that sets it all off.  But you'd be amazed at how often they can make small changes in drivers and suddenly apps can gain impressive speed increases.  But that kind of OpenGL tuning is very hard to do.  DS does have a few options on how it works with your OpenGL card (under Edit->Preferences on the Interface tab).  Finding the right combination for your video card can make a big difference in your interactive speed.

And if you are made of money, you can always throw a better card at it.  I'm currently using an nVidia 680 GTX with 4gigs of ram.  I recommend it easily.   But it wasn't exactly cheap.

-Matt