8800 stuttering in older games?? I assume that you have a 320MB 8800GTS...
Where the 120fps vs 144fps is concerned, not everyone has two 8800U's in SLi in the first and in the second place, if you want your graphics card to keep up with times (many games being released in the near future are sure to kill Joe Public's GPU, like Far Cry 2 and similar titles, not to mention highly anticipated titles like NFS:Undercover) you can't just stick to the same stuff for half a decade.
I'm all for holding on until a decent upgrade is available at a decent price but to say you have a pair of 8800U's in SLi (the scaling in many games leave much to be desired anyway) is completely beside the point. With that, I'm also certain that the HD4870X2 will launch at a much lower MSRP than the 8800U did (wasn't that 650USD or something?), nevermind that insane GTX280...