I currently run a gig of low latency ram, and until now, I have figured the leap to 2gb isn't worth it. I just came across an interesting article on tomshardware though, in which they explore that very idea. I've only read the first 1/3, but I'm already convinced and will consider upgrading my ram a lot more seriously now. What swayed me is that they proved that while an extra gig of ram may only show an average FPS of a ~5-10 frames greater, it provides a much more constant frame rate. That is, many less dips in FPS down to the undesirable regions. Here is a link to the middle of the article, with what I'm talking about.
http://www.tomshardware.com/2005/12/13/how_much_ram_do_you_really_need/page6.html
http://www.tomshardware.com/2005/12/13/how_much_ram_do_you_really_need/page6.html