In reply to JEF:
I have an etrex 30, I use it mainly for road cycling.
The 20 is the same minus the ANT+ ability (heart rate strap, temp sensor, and cadence) and barometric altimeter. Oh and it's a garish orange.
Free maps easy to download and install, takes AA batteries 24 hours battery life with rechargeables, robust and Waterproof (well tested by me - have ridden 27hrs in non-stop rain with no problems)