Anyone interested in how SDD (Solid State Disk) compares to HDD (Hard Disk Drive) can check out this (albeit biased) comparision of Samsung SSD vs HDD. Although it's done by a company whose object is obviously trying to sell SDD technology, their comparison appears pretty simple... two computers which look exactly the same, two fingers click the power button and time the startup time, etc etc.
This of course relates to the announcment yesterday from MacWorld of the MacBook Air.
SDD drives will put the end on mechanical hdd pretty soon now, personally i copmpletely support the take down of old hdd they were working long enough already and now they are no longer working as fast data carriers but are only slowing modern computers down. The modern ssd drives are fast reliable low power and quiet.