GPS is good, but I will always have a deck compass. (and I agree they are often hard to read. I don't want to place it closer to the cockpit because of metal bits that would interfere with accuracy)

I've had a couple of Garmin GPS units, both expensive "state of the art". A 76CS and after that corroded out I now have a Colorado.
I use the compasses in both, but I don't trust them. The units have to be level or the reading is wrong, Changing batteries, turning it on and off, random nonsense, seems to knock them out of whack and the reading is significantly wrong, like 30 degrees wrong. It's easy to re-calibrate, but still.... Also the Colorado has a curved back which makes it almost impossible to lay flat on my spray skirt.
A deck compass is consistently more reliable, (and useful to check the accuracy of the GPS compass.) The accuracy and signal capturing ability of current GPS units is phenomenal. I've even picked up signals in my classroom 20 feet from clouded windows, under a concrete ceiling. I've logged all day hikes and made maps from the route.

There's some terrific free software for GPS information. There are many different types, many can be found if you search for workout tracking software. They will break down a track into very small segments and calculate the speed for those segments. It's a great way to check the consistency of my stroke and speed over a long paddle.

Will