Yes - depending on model prior rides are logged and available for creating courses to ride against. You'll get both guidance to retrace the route and a "virtual partner" that runs against you - basically a second arrow on the screen that is your prior position at any given time. If you're riding stronger you will stay ahead of the virtual rider ... if not you'll have to work harder to catch up. The same is true for others courses/routes that are available through Garmin Connect, a web-based route sharing network.
You can also set up workout routines with specific time, distance, or HR intervals to follow. I have model 305, which doesn't track power, but the models (500, 705, 800) that interface with power (ANT+) might also have the ability to set specific power workouts too.
The older model 705 and the newer 800 are the most versatile. Also the most expensive. Both have base map options and detailed street info using micro SD cards. Other than the 500 route support is available so you can store routes in the device and recall them at will. The 500 supports a course/virtual partner, but does not store routes. It supports power for less cost than the 705 or 800, so a trade off there if power is your priority.
My 305 does not have a base map (nor does it support added maps), so I can't see streets. When data is uploaded or downloaded from computer, street/sat/hybrid views are available on the computer. When on the road I just follow a line on the screen. Using the zoom feature I can easily tell which direction and how far ahead a turn will be. If I go off course the unit will let me know and I then have to find ways to move back to the line. This also works when you intentionally want to deviate from a route - like starting a route from a different location ... just ride in the direction of the route until you're "on course" and then go where they went. I do this for courses others have ridden in a general area where I am, like from home or a hotel, etc. Makes it easy to go to a new location and ride at a strong pace without fumbling with cue sheets or maps. Definitely was a worthwhile investment for me.
