I recently switched to a Timex HRM and am very happy with it. I went with the Timex because it was the cheapest setup I could find for downloading raw
heart rate information to my computer. The polar HRMs that allow you to do that all cost more.
Its performance to date has been excellent. It rarely loses contact, and it doesn't seem to be bothered by cell phones or other people's HRMs. Downloading training data using the Data Recroder is a piece of cake. Timex monitors aren't the best if you like the fancy features of the Polar monitors (fitness tests, calorie expenditure, etc.), but they are great if you don't need that info, or if you already track that information using a different method.