Mousewait isn't very accurate.
The official DL app is great, and it's nice because you also have your reservations on the same app. It also links your Photopass Plus if you have one.
I have Lines as well and like it better on one thing -- it lists the times, including FP info, all on one screen, so you don't have to click through to the individual attraction to find what you're looking for like you do on the DL app, which doesn't list FP times on the main screen. So I thought it was much easier to use.
Having said that, I found one major problem with Lines. While I was there, it didn't accurately reflect when certain attractions were closed for parades and such. For instance, when I was trying to ride Storybookland shortly before a parade started, Lines was showing it open even though it closed an hour before parade time. So sometimes I used Lines then double checked DL.
I did find Lines often more accurately reflected actual wait times than the DL app. For instance, one time the posted time at Splash was 35 minutes. Both the DL app and the Lines app showed 35 minutes posted, but Lines also showed 20 minutes estimated actual wait, which turned out to be correct.