7200's rock big time - faster rotational speed = faster access to data as it takes much less time for the platters to spin so the head can read more data per second - i use them for streaming video at home and there is a major improvement in performance with the 7200's - ata33 and ata66 are burst speed indications - they will not be sustained so improvements are only marginal but faster drive rotation means more data can be pulled off the drive per unit of time - for a fun time go with 10000 rpm drives - have only played with one so far but boy oh boy they fly