I started my newsletter a little less than a year ago and at the time I set it up quickly because I was just experimenting with newsletters. As I've done more research and as I've seen my list grow to 350+ subscribers without an incentive I've decided to take my opt-ins more seriously. That's why I've been playing with OptinMonster and it's actually really great.
It's not a form builder and it won't make your contact form. What it can do though is give you a really nice interface to build an opt-in form. You choose a type of opt-in (sidebar, after the post, popup, etc), define some styles, tell it when to appear (only on this page), connect it to your list and press save. It's pretty slick.
This post though isn't about opt-ins. It's about being able to choose exactly where I want to place them. I write a lot about WooCommerce. In fact, 50 of my 192 posts are about WooCommerce. And I have an newsletter for people who want to learn more about WooCommerce so it makes sense to automatically add an opt-in form to any post that's tagged woocommerce. And that's something that OptinMonster doesn't handle natively. Luckily their support was great and pointed me in the right direction.