If you are going to make it Free, then please make it free without the obnoxious Pop Up.
When after using the free version if someone wants more features they will be happy to upgrade.
Look at the older software companys that have free versions. They are doing well selling their more advance products without bugging someone with HUGE popups.
Another suggestion would be to have all new news items come in on One popup instead of individual ones and make them smaller.
Thank you for a nice Rss Reader.