I can't work out where to submit bugs, but I have a number that I am going through and fixing.
First is the checkboxes on the subscription page. I have changed them so that the label tag is used. You can click anywhere on the checkbox title to switch its state, and don't have to get the mouse directly on the tiny box.
Also as a part of this fix the lists of checkboxes on that page have been put into an unordered list, rather than separated by breaks. This makes styling much easier, plus the form items are then inside block tags, which helps with standards compliance.
I don't know how best to submit these changes, so I am simply offering my MailPress 4.0.2 updated files for download: