I can't speak for VS Designer, but I've used Qt designer several times, and I find nothing wrong with it when the interfaces aren't trivial. Sometimes you need a massive form with dozens of widgets, in which case it's really helpful to lay things out visually, otherwise you risk getting lost in your code. If it's just one or two buttons there's less need for a form designer, though.
One thing I have noticed with Qt designer is that sometimes when you make a change in designer, it doesn't update the generated header right away, and you have to actually locate and delete the old one in order to make it do it's job. But that's not unreasonable considering the headache the designer's saving me from.
|I was planning on writing the layout code myself, especially in the beginning|
That's an excellent suggestion, and you should absolutely do that, otherwise you'll end up majorly confused in the future.
I think of it like this; consider mathematics, we know how to add, subtract, multiply, and divide, so it's no longer necessary for us to do it by hand, hence we get a calculator. So, it's really important that we get the hang of the underlying concepts first, else we risk being unable to create unique ideas in the future.
EDIT: For those who are interested, I found myself really comfortable with the concepts behind laying out Qt GUIs after following this tutorial: