So far I have found that 512 has been enough memory. If you have lots of programs open you could use more. I felt memory was pretty expensive currently. I upgraded to 60GB hard drive with the DVD/CD - RW combo drive. Seemed as if the common complaint on the first models of the Motion was hard drive capacity, so decided to play it safe. I don't watch DVD's etc so did not find any value in going to the modular multi format DVD writer.
Since I use the computer unattached from an external electrical source, I purchased the additional modular bay battery pack. Getting about 7-8 hours out of both batteries, when WiFi is turned off.
I would suggest extra stylus either Fujitsu or other in case you lose one.
I use their port replicator, but I think one could do the same thing for less money.