Which one? There isn't one just called lines and there are two with titles that are similar something like lines at wdw and wdw lines.
One is a subscribers app from the unofficial guide people.
I have tried several wait times apps, and my favorite is Lines (the one from the Unofficial Guide people). There is an active user base of people using the app regularly, which is key for wait times apps, since that's how most of them come up with information. But in addition to that, they have predicted wait times based on large amounts of accumulated data so that even if there isn't anyone who just reported a time, they can still give a pretty good estimate. That's crucial, because it's almost useless just to know that the wait for, say, Peter Pan was 35 minutes an hour ago, given the fluctuations of wait times throughout the day. If you are familiar with the Unofficial Guide, you know that these guys are big into data and statistics, and have been collecting information for years, so their predictions tend to be pretty good. They also include crowd calendar estimates and predictions in the app.
I wrote a review of it here, back when it was still in beta. My post is a little outdated (this was back when it was a web app and not yet on the App Store), but the main points still hold:
http://medgirl2001.wordpress.com/20...a-disney-wait-time-app-from-touringplans-com/
As for cost, obviously everybody has to decide what's worth it for them. It looks like they've upped the price to $10.95 for a 1 year subscription since I wrote that blog post, but you do get a discount if you have a current Unofficial Guide print copy (or one of their other books-they list the qualifying books on their website at
http://www.touringplans.com). I can't remember exactly what I paid, but I think it was something like $7 for a year? Maybe a bit less.
For free wait times apps, the one I prefer is Disney World Wait Times Free from VersaEdge software (they do a nice dining app also). This app is okay, but it is so dependent on who else is in the park submitting times that I just don't get as much use out of it.