i think the apple warranty is officially gone once you open up the housing (which i have done with pretty much every mac i have ever had) same goes for memory not bought with your apple 9first thing the service guy will ask you: do you have 3rd party ram installed?) anyway, mce has a install option and they provide a warranty (i think at that point the apple warranty stays in place as well)......
i use one drive for system and apps and the second for data, so while one drive runs C1, the other accepts the data...capture speed is faster, hw much? hard to say maybe 5-10%, it feels faster, but i did not time anything....
obviously the system is not faster (then a single 7200rpm) but processing and PS work is quite a bit faster (seperate scratch disc)....having 3-4 apps open at the same time while working with files is much faster....
for me it was a no-brainer, i almost never use the built in optical, i need the extra space anyway and the speed increase is well worth it for the money.....i haven't done the extra (3rd gig) ram upgrade yet, but will probably do that as well soon....
another option would be to create a striped array with the 2 drives which should really speed thing up, but i am too worried about drive failure...never happened to me, but in that case if one drive fails, all data is lost....and harder to recover....but that solution should give pretty nice capture speed....how much more? i find that we are still somewhat held back by FW400 anyway....