I recommend a garmin. I use the heart rate, cadence, speed and mileage features, along with downloading info to mapmyride (iphone, if we think we're lost). I have a garmin 305 (left over from running days) that DH just confiscated for Strava. Lately, I've been using mapmyride on my iphone. The ant+ handlebar mount is another $100, so i can't see my info while riding (jersey pocket). I also worry about battery life on long rides, so I'll be buying a Garmin 500(?) soon.
"Well-behaved women seldom make history." --Laurel Thatcher Ulrich
'09 Trek WSD 2.1 with a Brooks B-68 saddle
'11 Trek WSD Madone 5.2 with Brooks B-17