I use coffeescript both clientside and serverside (node). Since semantically the coffeescript maps to javascript almost one-to-one, the only debugging difficulty is mapping line numbers in the error output to the location in the coffee file.
Client-side is zero problem because the chrome and firebug developer tools jump you right to the line in the JS file, and you can figure out where the error is there since the compiled coffeescript is very readable.
Server-side has a slight hassle since there's no clickable link, so the line numbers don't help much, but a quick look at the stack trace makes it pretty easy to find where in the coffeescript its referring to.
Client-side is zero problem because the chrome and firebug developer tools jump you right to the line in the JS file, and you can figure out where the error is there since the compiled coffeescript is very readable.
Server-side has a slight hassle since there's no clickable link, so the line numbers don't help much, but a quick look at the stack trace makes it pretty easy to find where in the coffeescript its referring to.