i realize that. for servers, no 7200 even comes close.
for desktop, its a bit different, primarily due to usage patterns... and owning 5 raptors myself, its not like im dissing them or anything, theyre fast, even the oldest 36GB GDs are still. the point i was making though, is that the higher the density at a set rpm and area, the more data is able to be covered and accessed in a quicker amount of time. taking only 36GB of a 334GB platter for example, will most likely result in faster desktop performance than the same 36GB of a 36GB total 74GB raptor platter, if not at least on par.
taking a total 334GB platter, and comparing it to a 74GB raptor platter is questionable for performance though especially if the data is spread out across the whole platter... you still have to search across the whole 3.5" platter @ a slower 7200 rpms, just to locate that one piece of data, defeating any performance improvements it might have over a raptor. raptors are less affected by fragmentation though, for the same reasons listed above (smaller 2.5" platters, which allow for the higher rpms, so thats a multi performance improvement over 3.5" platters).
but, if you partition accordingly, the 334GB platter hdd should perform well in comparison to current raptors for desktop uses. the 74GB ADFD raptor i have, ive partitioned into several partitions, each up to 25GB in size. the fastest 25GB one for windows xp x64, a slightly slower 25GB partition for windows games, and still slightly slower 10GB partition for ubuntu 7.04. i left about 10GB unformatted at the end, as thats the slowest area of the whole platter, that i probably wont use for that reason. but this way performance is kept as fast as can be, and no real performance related concerns.
as far as future raptors, theres been rumors of a 15k raptor, which may or may not have pmr, sata300 is likely though, because as you said, the STRs may finally exceed sata150, giving them a reason to actually use it then.
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