I really like the Montana units, but in the end I went with a Zumo 350 for my 690e.  I use a Zumo 665 on my Harley and so I figured I'd be happy.  I was right.  Its supposed to be compatible with the topo maps but I haven't downloaded any yet.  It also has a fuel remaining calculator and a really bright screen.  It also came with a really solid handlebar mount that I would have to have paid an extra $80 to get for the Montana.