If you're directing that question to me, the answer is a definitive NO.

 Although a lot of marketing professionals will encourage the use of popups as a website designer with user experience in mind first and foremost I believe it is not a good idea. I've read how popups can get more signups for eNewsletters. No one is saying how many who feel forced to sign up for one ends up unsubscribing. I've never studied to be a marketing professional but I am a website user who also creates websites so people can easily navigate them and popups can kill a user's experience quickly and chase them right off your website. Unfortunately because of the nature of my work I can't turn on a popup blocker in my browsers so I get hit with them all.

User experience is damaged by popups. 

Imagine for instance that you're happily meandering down a road, taking in the scenery, and suddenly a huge brance falls in the road right into your path. Now you have come to a full stop and are sitting there, your peaceful drive disturbed and now you have to find a way around the tree or a way to move it out of the way so you can continue on your trip that was so annoyingly interrupted.. How does that make you feel? Irritated. Would you have been happier without this tree getting in your way? Definitely. I can't explain how annoyed I am when I'm reading a article and then instantly can no longer read it when I'm confronted with a popup. When that happens I just leave. I know a lot of people personally who do the exact same thing.

I've noticed personally that popups are becoming more annoying and larger. If I go to a website and I get a popup I will simply close the browser window and go to a complely different website where my browsing experience won't be so rudely interrupted. I'm a very busy person so I don't have time or the inclination to search for the little X to relieve myself of this annoyance, and some sites I've run into make you sign up for a eNewsletter to get past it. 

It now will hurt your website rankings

Because of the issue with overuse of popups some developers have taken a hard stance against them. Last year Google began punishing sites for using popups. This can effect your sites ranking on Google. You have to ask yourself is it worth the extra few people signing up on your mailing list to put a popup on your website just to have 3 times that many not find you because you're now on page 20 in a Google search?

Mobile issues

The majority of people on the internet today are getting there on their mobile device. This is causing havoc with the search engines used by mobile devices, sometimes making the user unable to get past the popup and causing them to seek help from their device provider to remove them. Apple has a entire section on blocking popups and how to fix it if you're unable to close a popup in your mobile browser. Scammers are now using popups and will completely lock up a mobile browser. If you search for information on popup ads on mobile devices the majority of the results are how to prevent them and the problems they're causing.

I could go on and on but to put it in a nutshell it's not a good idea. A site administrator won't know how many people like myself will just leave the site entirely because of the popup so there are no solid numbers on that.  If you want people to sign up for you eNewsletter I would suggest placing the signup in a prominent place and offer them deals on signup or a special discount or mailer. That way you guarantee the people who do sign up for your eNewsletter are actually going to read it when it hits their inbox and not just delete it or unsubscribe.