I don't really have any interest in the buttons or boxes (so thanks for separating them out), but the columns add-on is fantastic!

We make sites for very very low-tech clients and we've had lots of trouble finding a way for them to have more complex layouts. Tables are a huge mess, and very buggy in WordPress, and column shortcodes aren't easy for regular people to get their head around. Being able to created columns so simply in in the visual editor is a big deal for us.

The only issue I've notice so far is that copying and pasting into a column can go kind of funny sometimes. I've noticed that sometimes when pasting into a column it would get pasted outside it. I also tried copying text from a half column in one set of columns and pasting to the left column of a 1/3 - 2/3 set. When I pasted it ended up pasting into the 2nd column, rather than the one I was pasting into. I could see this being a TinyMCE issue though.