Not exactly true - the 500 shows you a plot of your track and it'll tell you to turn... as you go through the turn. I seem to recall getting "turn now" type stuff when viewing the normal bike pages. Mine's pretty new and I haven't explored every possible configuration yet though.

If you really want a visible map, the 800 is probably the best option. The 500 has just enough capability to use in a pinch and then of course, you have your ever present smart phone with google maps.