I have a Garmin Zumo 550,
6 months ago we went on a 1300km remote desert trip, with not not much to be seen on the horizan at times and not to much to identiy tracks and direction, this thing was a savour, even though we also carried maps, confidence was certianly through having the GPS. I also installed the offroad maps into it as well.
It is disigned for bikes, water proof, can be operated with left hand whilst riding and touch screen can be used with gloves on.It came with a bike kit and handle bar mount.I also use it daily in the car around the city as a navigator. Great bit of gear. It may come across as a bit bulky on the bars to some, however I like the larger type units, easy to see and read. heaps of other features also.The other 2 gps on the trip were hand held type and compact, and you had to feed them with batteries, they didnt seem to have much track detail either.They could well of been older gps units also.
I have had it submerged under mud and water, and have given it a hell of a test with jumping and extreme vibration on the bike with nasty corrogates in tracks for long perods of time, it has never missed a beat.it was hit fairly constantly by branches and scrub to the piont where the left sleeve on my riding jersey was just about gone and almost blood coming from the knuckles.
If it is mounted high and forward on the bike , the odd occational branch hit the retaining bracket and dislodged the GPS and sent it cart wheeling down the track next to the bike a few times. still it kept on going. All i done was placed a peice of tape over the clip on the retaining bracket to stop it and never had any problem after that. These were pretty bad conditions and there was a lot of other gear and equipent failures also.
It came with the car kit and wiring for the bike,you can even use it in the boat with marine charts or maps as well.I installed oztopo v.2.1 maps.
It certianly exceeded my expectations as a durable product in an offroad enviroment.I started to have a look about for maps , some are free off the net and others you purchase. Some maps for the gps had different bits and peices and there was a heap of opinions out there also about it all.
I recon the amount of fuel wasted when exploring and getting lost, a gps can quickly pay for itself and saves you the time as well.
Hope this helps a bit..