The 62 series should be shipping in a month or so, Q3 2010. It's basically the same as the 78 series (marine version) which is available now.
The Birdseye subscription can be useful to get a bit extra situational awareness in unfamiliar areas, especially when hiking / when far away from any roads or trails. It lets you "see" nearby terrain (sandy, thick forest, rocky, etc.) to help make navigation decisions.
Otherwise the benefit is probably marginal especially if you have paper maps and mainly navigate by roads / trails. I think for most people it's a "nice to have" rather than a must have. Also worth noting that the quality of the Birdseye imagery vary greatly depending on region.
Other than Birdseye, the 62/78 also support custom maps, have better screens (compared to the 60/76), are faster, and can store 200 tracks vs. 20 which is a big benefit if you're off-road a lot. They also have a 3-axis electronic compass (the one in the 60 is useless when the unit is not held perfectly horizontal).