I've started using a chest strap and it does seem to give me slightly more realistic readings. I do seem to have a particularly fast ticker, but my watch recorded 212 the other week on the climb up to stoodley pike. Based on that I would have expected to chucking my guts up but I dont even remember working particularly hard at the point it was recorded.

In reality with the chest strap I think my max hr is more like 205 (still seems to be pretty high for a 32 year old though).

Also, I find with a chest strap there doesnt seem to be as much lag. With the watch I would be running up a very short incline and then recover on the flat over the crest but the hr wouldnt really increase on the screen until I was already well over the top and easing off on the flat.