I've seen a few 9600GTs around for sale (and heard of some to come) that have 1GB of memory as opposed to the default 512 MB.  I haven't been able to find actual benchmarks that compare the two versions, so does anyone know (either from personal experience or from some benchmarks I haven't seen) if the 1 GB of memory makes any real difference, and if it does, is it worth it?

Here is a link of 8800GT(which performs like a 9600GT in many times) 256 vs 512 vs 1GB,it will help u alot:
http://techreport.com/articles.x/14230

Typically at resolutions greater than 1920 x 1200 (24" screen) you

get higher FPS with 1Gb especially with top end cards, (9800GTX and up) but at those resolutions the 9600GT won't make use of the extra memory due to it being just a mid range card.

It makes little or no difference.
 
Given the option of a 1GB 9600GT and a 512MB 8800GT, the 8800GT is the better choice.

The 9600's g94 core, which is exactly half a 8800gts g92 core overclocked, bottlenecks ram at high resolutions. You'd need at least a g92 8800gts to run at the high resolutions needed to take advantage of 1gb ram.

Basicly this is the Deal.
 
512mb = less memory to cache textures and everything, but faster access time.
1024 MB = more memory to cache textures and everything, but higher access times.
 
I remember a old ati with 128mb GDDR2 a 9600XT Gamebuster that kiced ass compared to other GPUs with 256 and 512.
Low access times and a really fast memory for its time. Sometimes you much choose. The perfect solution or its really expensive or doesnt exist.

The 8800GT link Maziar posted is a great one to see how little even the 8800GT benefits from 1GB.  The only review I have seen of a 1GB 9600GT is tweaktown with an OC'ed MSI.   For the life of me I can't seem to find they mentioned the clock speeds of the other two 9600GT they used, which is much needed info??????? http://www.tweaktown.com/reviews/1 [...] index.html
 
edit: I think the Vvikko Turbo is clocked 700/2000 vs the msi 700/1900.  
http://www.vvikoo.com/product_detail02.asp?id=38