When it works it is really good.

The instapage plug-in is amazing when it works. There are bugs and instances of the pages not working. Some issues are fixed quick and they have a very friendly support team. It does suck to pay for ads to your website only to have the wordpress instapage not load or not work. When a page breaks it has a giant blue page that includes the logo and says you’ve discovered a missing link. One of my wp instapages has been broken for weeks and no solution. Other ones work great and no problem. They have a free trial so try it out. It was recommended that I don’t use the plug-in and instead redirect customers back to an instapage hosted lander.
Keep a close eye on your landing pages built with this, if working you’ll be happy with it.