The current checkboxes in the regular plastic client are borderline unusable from both a usability and visual feedback perspective.

By contrast, the Gluon client hits the mark with its checkboxes. It has much larger checkbox size that are far easier to click, and checkboxes that are coloured in when checked as opposed to a tiny black tick mark that is practically impossible to see when dealing with a larger changeset (I've lost count now the number of times I've checked in files I didn't intend to include, simply because the client decided to check them automatically and I couldn't tell).

Having the same checkboxes in both clients would help remarkably with the checkin process