I'm running a TEC and yes it is not for heavy overclocking, but it is definitely a good alternative to watercooling/high end air cooling. More specifically you need to research before hand at the thermal output of your CPU and the max dissipation of the TEC. My Ultra ChillTEC runs a q6600 @ 3.4ghz with 1.22vcore usually 40c idle and 60 load. The other thing you have to look at is intel's future CPUs are not going up in thermal output, their going down due to the decreased die size. Such as for example my q6600 G0 at stock has a 95w thermal output, the Q9450 has the same stock 95w output but operates at a higher clock on stock. Theoretically as proven with the E8400s this could make it an outstanding overclocker, but then again the 8 multi is like a slap in the face.
Boiling down to it, yes TECs are more expensive and could probably be beat by a blazing air cooler. I've had both water and air, my pump died...so I looked for something that was a failsafe. If my TEC completely stops.... it still has a gigantic heatpiped air cooling system which does a good job. If your pump dies, your SOL.