(someone) appreciates (something)

When you "appreciate" something, it means that you notice it and are thankful for it.

You say "I appreciate ___" or "We appreciate ___" when you want to thank someone for their actions. This phrase sounds more clear and explicit than just saying "Thank you for ___".

An example of this is when your child confesses that she broke something, and you say:

I appreciate your honesty.

bust (one's) ass

"Busting your ass" is an idiom that means "working really hard". 

I busted my ass waiting tables and working construction to pay my way through college. 

I know that all of you have really busted your asses on this project, and I really appreciate it.

This is a colloquial expression that you use when talking to people you're comfortable with. The word "ass" is a mild swear word. You probably shouldn't use it in formal situations.

There's also another meaning of "busting your ass", by the way. It means to injure your butt by falling:

You remember that time when you slipped on the ice in the front driveway and busted your ass?

I know that you've (done something)

You can say "I know that..." to show someone that you understand their feelings:

I know that you were disappointed that we didn't get a chance to visit the winery. I'm sorry about that.

I know that you must have spent a lot of time putting all of these notes together. Thank you so, so much for doing that!