I have the Polar FT7 too, and just run the chest strap under water at the sinks at the gym just before I put it on. That doesn't bother me because I am drenched by the end of a workout anyway (sorry if TMI). The chest strap is stretchy and comfortable, and doesn't have to be anywhere near as snug as the bra strap just above it. The batteries in this model of Polar is user-replaceable, and I believe all models of Polar HRMs may have user-replaceable batteries by now.
I chose the FT7 because Polar is supposed to make the best HRM's, and because the FT7 provides the output that I want. Originally I was interested in the Polay FT60, because it has wonderful reviews, but I decided it was a more expensive, more complex HRM than I wanted.
I like wearing an HRM during my workouts. It has performed flawlessly thus far, never having even the slightest difficulty in picking up my heart rate. During the workout, I can see my heart rate on the watch part and that helps me to decide if it is time for another set yet. Also, all the cardio machines at the gym pick up the heart rate transmission and display it without the need for any action on my part. I find the HRM to be very motivational.
It also helps me to recognize when I might be overdoing, and after a workout I can see if I slacked off or did well.
Unexpectedly, I found that my average and maximum heart rate actually are higher (for me only) during weight lifting than they are when I am riding an exercycle for the same amount of time. That leads me to believe that perhaps for me (only), weight lifting in the way that I lift weights may provide some cardio benefit as well.