I have 8GB RAM + an Intel SSD in my MacBookPro. There are very few physical reads - most of the data I require fits in filesystem cache.

When there are physical reads, the response time is awesomely fast. An IO is less than 1ms. For the drive included with my machine an IO was ~10ms.

It's response time (not throughput - as seen in many benchmarks) that makes you want an SSD on your desktop.