We've used hardwood chunks for a dozen seasons. Our wood heater is mostly to take the chill off morning and evening in the spring and fall on the coast of Maine.
Hardwood heats up fast which is what we want in the morning or evening, and it goes out pretty quickly too which is handy to get going in the morning.
An option I haven't tried but sounds good is using the new bio bricks for woodstoves. A compressed wood product, you can cut or chop them into sizes that fit your stove. I can't imagine pellets working, we burn them at home in a pellet stove
We keep an old sailbag filled with hardwood chunks and kindling in a hanging locker and fire the stove often.