Finally, I got an answer: those pools get near the boiling point of water, but no further, and you're not going to get enough energy for the generators to pay for themselves unless they're running on super heated steam. Yes, there's a fair amount of energy there, but it's not concentrated enough to use. Sigh!
When "spent" fuel is removed from the reactor, the fission reaction has stopped, but the residual heat from the decaying by-products would cause the fuel bundles to melt. (This is what happened at TMI- The reactor was shut down and no fission reaction was underway, but the water level got low enough to uncover the fuel bundles, and without water to carry away the residual heat of decay, they started melting.) The water in the spent fuel pool would indeed get near the boiling point of water if it were not for the constant cooling of the pool, but letting the pool get that hot wouldn't be a good idea, though, since the spent fuel pool at your average nuclear power plant is about the size of an Olympic swimming pool, and many activities take place in the same building (which is separate from the reactor containment building), such as the preparation of new fuel rods (they are stored in the same pool, but shielded from the spent rods), storage and preparation of the dry storage casks that the oldest spent fuel goes into, and temporary warehousing of low level radwaste, things like contaminated water filters, protective suits, decontamination materials, etc. Steam from that much hot water would hamper activities and be detrimental to everything inside of the spent fuel storage building.
After a number of years, the short lived by-products have decayed enough that the oldest spent fuel bundles can be stored in shielded casks for dry storage. Sure, they are still warm (thermally speaking), but not enough to melt or otherwise cause damage to the container in which they are stored (as the fuel rods are still smokin' hot radioactively speaking).
I think some people have actually proposed ideas to harvest the excessive heat using waste heat recovery technologies like thermocouples, low pressure turbines (running on ammonia), stirling engines, preheating the feedwater going back into the steam generators, etc.