Hi Kent,  
 
  did you have a power meter system before this?  Is this the Quarq CinQo unit?  (http://www.quarq.us/)
 
Let us know how you like it, I have no experience to offer I'm afraid, a bit out of my league with this stuff.
Now that I have a small wheeled FWD bike I don't think either a PT or a Polar would do much for me. Like you a crank based system will need to support 165mm length.  
 
Take Care,
Nelson.

Hey, I can logon again! Couldn't for a while.
 
I've been running the Quarq power meter on a Lightning 165mm carbon crankset for about a month now. I'm using a Garmin Edge 500 head with it. Very educational. As to the hardware, Lightning delayed the thing by well over a month. Probably best to not go into that...  Quarq, otoh, has been absolutely fabulous to deal with. We had Lightning send the cranks to Quarq, who installed the power meter spyder and calibrated it to the rings I chose. Then, since I had already disappeared off to Florida in the meantime, they shipped the unit here with no difficulty. Again, great customer service. I then had to get Lightning to send yet another part - they sent two right bearing cups instead of one of each, so a little more delay. The crankset went together very easily though. Did I mention it is *light*??? I suspect that the left FSA Gossamer crankarm that was on there weighs more than the whole crankset with power meter.
 
The Quarq unit comes with it's own cadence sensor. iIt's required for the power meter to work or at least transmit any data. You have to attach a magnet to the bike. You can epoxy one to the frame or they have a ring mount that slips behind the bearing cup with a magnet on it. The Lightning cups are larger diameter so it doesn't quite fit by about a mm. I modified it a teeny bit to make it work. Nice, clean fit otherwise. Looks great. Quarq is thinking of making a unit for mtn bike racing, which would be a triple, and they said they would look at adapting it to be able to run a road triple also. So there's hope...
 
As to use, I was really surprised at how much power I can generate. I had an idea that I was fairly strong for an old guy but I peak around 1100 watts, usually on launches when I'm spinning up around 130rpm. The cold weather put a damper on my power output but it appears my 24hr-type average output is somewhere around 150W and my fast, hard century output is somewhere around 200-220 average.  I can sustain 450w for about 2 minutes, 500 for about 1.5 minutes. I routinely crank the bike path overpasses at 700-800w (I still haven't seen those hills the locals keep pointing at), cresting them at 20mph (except when it's cold...) and I'm up around 800+ when I hit 35mph with no headwind. I always thought 500w would be a lot of power but I'm not even wound up when I hit that. So I've mostly been trying to get a good baseline on what I do and what is required of me in order to start working on a training program (if I ever get around to it). I think I probably generate enough power but I have to work on endurance at high power levels. If I get stronger, I expect my feet will be the weak link.