Don't have one yet for my bike but here is a positive review of the Garmin I5 on webbikeworld.
http://www.webbikeworld.com/garmin-gps/garmin-i5/garmin-i5.htm
They also reviewed the new TomTom Rider but it seemed mixed.

Side note: i strapped my runners watch GPS to my handlebar this weekend to check speed. It fit and worked great! Of course no map but it verified my Triumph speedo is 5mph fast around 60+.

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