i had the same problem with my original 36GB GD raptors on a generic 350watt psu, neither of them would power up at first... raptors consume more power than a standard 7200rpm hdd does, which is the first thing... so it could simply be your psu isnt outputting sufficient power to it (and i had nearly the same problem again with the 74GB ADFD i just purchased a few weeks ago, this being with a 600watt x-finity psu, the whole computer wouldnt even power up, oddly, until i disconnected some other drives, rearranged the cabling, and then it worked... at first i thought i had damaged something, but, that was far from the case)
make sure its towards the beginning of the power cabling, or at the very least not daisy chained behind other components on the same length of molex/sata power connections from the psu... if it is, most likely it wont even power up (as youre seeing)
try disconnecting other devices from your psu, and move the raptor up closer to the first psu molex/sata connector (trying different connectors that are closer too), at least so you can check if it really is dead
if a raptor is powered, its fairly audible when it powers up (in addition to standard hdd vibrations)
edit: as far as being worth the money though... if you have the money and the desire for alittle bit of extra speed? yes. even the oldest 36GB GD raptor from 4 years ago is about the same speed and slightly faster than a 400GB maxtor hdd from just last year... ...the 3 ADFD raptors ($100 36GB, $150 74GB, and $200+ 150GB, all of which are the same speed, as they each use the same sized 74GB platter) range from 20-40% faster than the 36GB GD raptor for STRs (depending on the benchmark too), and all raptors are twice as fast for random access times compared to other 7200s... ...so, in the end its only worth it if you have the money to spare, and arent so concerned about capacity... even as just an OS hdd, a raptor is definetly the way to go, or any raptor really for that matter, simply due to the 7-8ms access times (10Krpms), which makes for a more responsive OS anyhow.
with the possible exception of the raptor you received (assuming it really doesnt work), raptors are more reliable than other consumer 7200s, due to them being designed for use in servers for 24/7 operation (built in heatsinks because they do get hot, drive mechanics to compensate for vibrations in server racks, 1.2 million hour mtbf, and, other things i cant remember off the top of my head... well, a 5 year warranty too, but thats pretty standard, but it pays off if you need to rma it, such as in your case maybe (if the warranty is still valid now)