Me too. I just quartered a kabocha squash for dinner tonight with my fillet knife only. It's just not really long enough to handle a watermelon or large squash (like a Hubbard), but after I've cut the behemoth into manageable units, I always go back to the trusty fillet/boning knife. I even use it on butternut squash. I consider it my best friend in the kitchen.
It's the best for disjointing poultry and cutting between vertebrae and such, as well as making thin, precise slices, or curved cuts, like cutting watermelon flesh from the rind. I own a cheese slicer, the kind with the thin wire and the roller on a handle, but never use it because I can get thinner and more uniform slices with my knife.
Mine's a cheap one too, Pinnacle Cutlery stainless and made in Taiwan. I picked it up at Dollar General many years ago for the sum of $2.00. 
The blade length is only 4-3/4" with the sharp edge being only 4". It still does 99% of what I need to do, and I find it easy to control, and therefore safer. I fervently wish I had bought more when they were on offer, just in case something happens to my little daily companion and workhorse (pony?). It still sharpens up to almost razor sharp and holds that edge respectably well. I baby it though, and no one else is allowed to touch it, much less use it.
