Depends on what you're playing and how long you think you'll keep this card.
Games like Skyrim for example, played @ 1920x1080 resolution with graphic/texture mods will easily eat more than 1GB of video memory.
My GTX 470 SLI setup actually has a hard time keeping a steady frame rate in Skyrim because it uses every bit of my 1GB of GPU-RAM. So occasionally it'll stutter as it loads data.
At this point I'd suggest a 2GB video card (primarily if you'll be playing at higher resolutions). Games are beginning to get to that level.
Normally a 2GB card would cost more. However, the 1GB card you're looking at has an upgraded cooler. So that's why the price is basically the same. Get the 2GB version.