After reading more of the replies, I think it really comes down to two things - what you shoot and how you shoot. If you typically shoot from a stationary location (hide, dock, road, etc.) and shoot subjects that are more approachable, then a gimbal makes a lot more sense than handholding or a ballhead. If you move around a lot, shoot in areas with very little cover and/or shoot subjects that you have to stalk or ones that move erratically, a monopod or handheld works best. I find myself in the second camp with the majority of my shooting and rarely have the chance to set up a tripod, so handheld IS makes sense. If I had a 600+mm lens and could set up somewhere, I'd definitely get a gimbal.