I have a forerunner 10 (second hand for £60).
It does what it does very well and I like that it's small-ish (could wear it all day everyday if you were so inclined) and also waterproof.
Having said that if you want a HR monitor (or would like to in the future) then a 110 is the way to go. I may eventually move up but the 10 has proved to be a pretty cost effective stop-gap for me as I got it fairly cheap.