I think this new Garmin is great. I now use a ForeTrex 101 to see the routes I ride, to study the data on a PC, and of course not to get lost in the middle of nowhere. Also I use a CS200 for HR, and more accurate speed information, etc. But unfortunately none of my computers is perfect. Foretrex loses signal in the woods, the elevation data is not accurate, and CS200 does not work if you pass under high voltage power lines, and needs to be reset.
As far as I understand the new Garmin is going to be much better with a more sensitive receiver. I think cadence kit includes the magnetic speed sensor. It says that it is self calibrating so I guess it calculates the tire circumference by itself using GPS speed data. I think it is a great feature.
The manual is not there, but it will be on the Garmin site soon I guess. Can't wait to read it...
Also I think it has a reasonable price. The 305 model is $313 CAD for preorder at
GPScity.ca