Great plugin but difficult to customize

It works great, and I like very much that its design is flat.
Unfortunately, it is a bit difficult to customize, apparently simple things like putting two fields next to each other is not easy to achieve. I am also having a lot of trouble to customize the checkbox so that it looks clean in every browser, instead of displaying the default one. I wish it was a bit more comfortable to do such apparent basic things, and not rely on additional plugins to do that.