I purchased a Garmin Edge 800 in 2012. The 800 has a map display and will give you turn by turn directions. The 800 is geared somewhat toward training, laps, etc. But it has a lot of features and I find it very suitable for the recreation riding I do. There are so many features and screens, it took me a while to learn how to use it. The screens are customizable, letting you add/delete pages and put what ever statistics you want on each page. The screen is touch sensitive for swiping. The 800 and other models allow you to download GPX and TCX files for routes, or courses in Garmin parlance. The Garmin Edge 810 is new this year. Go to Garmin's web site to learn the differences. GPX files are available from the CD, or now the RBC web site. You can also create your own using sites such as Garmin Connect, Map My Ride, Ride With GPS, Bike Route Toaster, etc. Ride With GPS has some tips on how to configure the Edge 800.
When I bought my 800, I tried to save money by buying just the GPS, not the bundle. The stand alone Edge 800 comes with only a very basic map, not suitable for bike riding. I also thought I could use one of my many heart rate monitor straps. It turned out I needed an ANT+ heart rate monitor. After discovering these things, I bought a map chip and also an ANT+ heart monitor. I would have saved money if I bought the bundle which includes both plus a cadence sensor. You can purchase the stand alone Edge 800 and then buy a blank 2GB microSD card. You can down load Open Street Maps for free onto the microSD card instead of paying Garmin's map.
The 800 can be use on multiple bikes, or even other non-cycling activities. I took mine on a couple down hill ski trips and clocked over 50 MPH!