GPS units

I got lost so many times heading to Quadancers house that I decided I need a GPS unit. Tax rebate is burning a hole in my pocket. I'm looking at a Garmin 620 which is also a marine (waterproof) model cuz I'm in a boat often enough to want one there too. I looked at the Garmin 3597 also, and the Garmin 660, but really feel I want a 5 inch screen. Probably would use a RAM mount. Mine gets put on an "09 Heritage.
Anybody care to share their experiences and identify the models they have?

Hey Dan, dunno if you noticed mine, but the way I have it, it's invisible. I just put the strap underneath the bar clamp to center mine, and put it
in my field of view. Well, and for looks too. Here's the mount:
http://www.ebay.com/itm/Bike-Handlebar-Strap-Mount-for-Garmin-Nuvi-30-40-50-50LM-3450-3490-3750-3790-GPS-/360447972226?pt=GPS_Holders_Mounts&hash=item53ec5f9382

It was only $7 and change when I bought it. Here's a pic of it just before I centered it; I guess I forgot to take another shot:

So which Nuvi model do you have?
Have you had any problems with it not being waterproof? What do you do with it when it rains really hard or for a long duration?
The now $12 mount looks great, Who manufactures it? I need to check what other Nuvi models they have a mount for. Thanks.