ClevelandGuy: I have been messing with them lately. I've tried the following monitors:
Vetta bike computer with HRM - shows current and average HR for the ride. Very simple to use.
Sigma PC-1600. I found it difficult to navigate. Press this button to access the function then this one to get to that function, etc. Sold it on Ebay the other day.
Polar M21. I haven't used this one much my wife Donna is checking it out. It seems pretty good so far.
I'm currently using the Performance Axiom 600. It's pretty nice though for some reason I keep deleting the average and max HR settings before I can log them
I especially like that this HRM shows what percentage of your max the current HR is. I know at a glance if I need to pick up the pace or need to cut back a bit.
If I could find a cycle computer that had cadence and HRM I'd probably use one of those instead of a separate HRM and computer.
One quick word of caution. Don't become a slave to the HRM. Use it as a tool and don't let it rule your entire ride.
Zack