I liked mine a lot until I get a "point and shoot" style video camera and, and then my new DSLR -- now I pretty much use mine for underwater and for buddies that want to shoot some video while we are floating as it is really, really easy to do so. GoPro's are GREAT for what they are meant to be used for and for the most part they aren't exactly meant for fly fishing where you want to get "pretty" video. They are great for getting footage from a boat because of the super wide angle though.
I am glad someone said something about the file sizes. I have had a TON of emails over the last few years about people having problems with the video playback and editing of their GoPro footage.....most have either had to buy a new computer or they simply shoot video on the GoPro for the fun of it because their computer just can't pull off the Hi-Def playback/editing. So MAKE SURE you have a newer computer and a video editing software that can handle the file type and size of the GoPro. You will really need a minimum of 4gb of ram and a huge external hard drive to hold all of your footage so it doesn't fill your computers hard drive. I have 2 external hard drives with well over 1tb of footage I am sitting on right now. I 'do' tend to spend a ton of time on the water so that means I have more chances to shoot video.....which means I have a TON of footage, so if you are just going to grab some footage here and there it may be a little different.
For what it's worth, I will probably be doing a couple of classes on video at the Southern Council Conclave this October in Mtn Home.