Well, I have a really hard time classifying what I like and don't like in guard. I used to say that I didn't like slow shows, but then I saw BD's last world class winterguard show and I changed my mind, sort of. I think that anything works if it's done well. Some things, like slow shows, are harder to pull off than others.
With the whole props thing, I personally don't really like them. However, sometimes they are the better design choice. If a guard is not that strong, sometimes props are necessary to cover that up. If a guard is truly good, though, props should not be necessary. The only exception I would make to that rule is that a prop is only as good as how you use it. When a guard that really is good enough that props shouldn't be necessary and is just using them to take up space, that doesn't work. When the prop makes the work more difficult or can be spun with as much technique as normal equipment, then it works. The commas, I think, work. Backdrops just sitting behind a performance do not.