Evaluate hill gradient
There are various web sites that might help.

I use one called http://ridewithgps.com. You need to register on it but you can get quite a lot from a free account.

Does your GPS device output GPX files? If so, I think Ride With GPS can suck them in. If not you might have to put your route into the site manually (but this is easy enough).

But what you do get on your route is a display of the gradient (you hover over different parts of the route to see it). 

For example, I did a quick ride yesterday afternoon, here it is:



I have a pay account with these people but I'm fairly sure you get this page with the free account too.

Any good to you?

Just added another image - didn't realise SE was going to reduce the main one so much. This is just a zoom of the bit with the tooltip. Note also the blue dot in the corner - this is the location on the google map which corresponds to the crosshairs on the elevation plot.