Against this forum's advice, I bought an older wired Powertap SL (black end cap with two screws) about a month ago. It's working out alright for me so far, but I tried washing it the bike, and spent two days drying out the hub to get accurate data again!

It's shaping up to be a rainy summer, and winters always see a lot of rain riding for me. I can tell this is going to be a problem. Since the Powertap I got is so old, I figure I can probably sell it along for what I paid, and get something more reliable.

I'm looking at the Polar, but I've heard mixed reviews. I'm not a sprinter, so the ability to get an accurate maximum reading isn't terribly important to me. I've heard that the average over meaningful times is pretty accurate, which is what matters.

My question, though, is how well does it hold up to year-round all-weather riding? I ride in the rain and hose my bike down frequently. It's a tool, not a jewel; it gets maintained, but not babied. I've accepted a certain rate of attrition with headsets, bottom brackets, and cables/housing as a result. Adopting that mentality with power measurement would be too expensive, though!

I should mention that I'm on a tight budget, too - an SRM/Quarq or even a nicer Powertap really isn't in the cards.

You can improve the weatherproofing of the old PTs with some work. First, make sure it has both the inner and outer o-rings present, as well as an o-ring on both screws. If it doesn't, remedy that first. Then, you can use a good layer of grease around both the inner and outer lips of the caps to seal against the o-ring. They didn't design the o-ring seal very well; it doesn't have a groove to capture/compress the o-ring, but the grease usually seals it decently.

Finally, if you really get annoyed, you can caulk the cap with clear silicone..that worked very well for me and I'd just cut the silicone when I needed to pull the cap to change batteries.