nothingmuch wrote a review of Polar AXN 300 Altimeter/Heart Rate Watch on December 3, 2008
Feature wise this watch is great.
The construction is pretty bad though. I have a fairly thin wrist for a guy, and it was never really comfortable, but despite all it's bulk two of the buttons broke and the watch became unusable within about 3-4 months of use.
This is not abuse, mind you. I was hiking and would use the buttons normally, and their plastic just cracked down the middle. I don't think I ever hit it against a rock or anything.
In short, be gentle and the watch will work well if it fits you.