I'll throw in a quick vote for a plate chiller, since it doesn't seem to be getting any love in this thread.
I have a DudaDiesel B23-A 30 plate chiller shown
here, and I love it. A plate chiller is a pricier option, however, as I also purchased stainless steel quick disconnects for all my connections, plus a Chugger pump to push the beer through the chiller. I've also installed a ball valve and thermometer on the output port, so I can throttle the beer throughput as necessary to get the desired wort temperature coming out. Also, it's more of a headache to clean than a simple immersion chiller.
That said, the performance is dramatic. When the groundwater is cold (as it currently is), I can push 10 gallons of wort through the chiller with all valves wide open (basically moving the beer as fast as the Chugger pump is capable), and the wort comes out of the chiller right around 60° F, pretty much perfect pitching temperature for an ale. This takes about 4 minutes for 10 gallons, 2 minutes for 5. If I'm brewing a lager, I throttle the output a little to slow the wort down (while still running the chilling water through at full speed), and the wort comes out of the chiller at 50° F. For 5 gallons of lager, this might take 3-4 minutes. It's so much faster than an immersion chiller, and avoids wasting nearly as much chilling water (nor do I have to stand there and stir my wort for 5-10 minutes).
For cleanup, I recirculate hot PBW backwards through the chiller while I clean my kettle, then blast it clean with the cold water line from the tap to rinse.
Just another option to consider.