Yeah, a big stump takes hours to grind but has still been easier and faster than any alternative I could do. A 30" oak stump that's 1' above ground would likely take me 3 hours to get it below ground. Most smaller stumps are usually good for an hour.
And I've done lots of em. Just takes patience, some noise-cancelling headphones hooked up to music, something cool in the cupholder, and more patience. Before I got the PT, the stumps just stayed there, which is why "I've done lots of em".... 30 years of accumulated stumps.
Phil