Concerning this, I ran SL with an Intel Extreme through 1.4 with no lighting, shiney and medium land, tree and av settings. My standard draw was 64m and i kept particles at 1024. It also helped to keep the bandwidth lower than the connection could actually handle.
When 1.5 was released, I noticed a huge difference in speed; in fact I hesitate to use the term "speed" to describe it. The Intel was obviously not going to cut it anymore so I finally traded in my laptop for one with an Nvidia Geforce Go. It's still going strong with shiney, full land rendering, 128m draw and max particles.
/clap