I love mine. Here are the most common negatives i hear on the various forums...
1. Smoke flavor not as strong as stick burner - this is subjective
2. Not as "good" a smoke ring - I get a very nice smoke ring, and smoke ring shouldn't impact scores (theoretically)
3. Mechanical, so parts failure can be an issue - always a concern with anything that has moving parts/electronics. Some teams carry spare parts.
4. Need power - If power fails at a comp you could be sunk. Most teams carry either a battery/inverter or a generator
I think that covers the most common ones. I'm not getting into the whole "cheating" or "skill set" argument. We've beaten that to death multiple times :-D