Ok, so here are my findings so far with regards to searching for FP's (and I have already emailed Disney with my feedback).
Personally I have found the app super fast which is awesome!! Previously I would get about 25-30 refreshes per minute and with the update I have easily been over 40/minute.
1) Huge problem is that when you search for a FP and it shows up you have a very high chance of still not getting it (if we're looking for FP's without great availability). When you refresh and see a ride/time that you want previously you would click on it and be all good. Now it runs what appears to be a second search/refresh once you select it and you may still lose the FP. I have been hitting the time in under a second from the FP showing up and missing far more than I get for hard to get rides even in that 1 second time. If you have to scroll at all it becomes even harder because that takes another second or two.
2) If you are modifying and two times show up, you click on the time you want, and it goes to the confirmation screen...watch that screen CAREFULLY!! Let's say a 2:00PM and a 10:00PM time show up and you choose the 2:00. If that FP is now no longer available it will automatically choose the 10PM FP for you and go to the confirmation screen with the 10PM FP selected. There will be a notice at the top that they have chosen a different time for you but if you are going quickly or only half paying attention that can easily be missed.
3) When modifying, when you select a new time the confirmation screen just keeps spinning and never confirms the new choice. Do not panic. Just click on My Plans and you will see the new FP has replaced the old one even though you never got it to show the confirmation.
These are just a few quick things I have found while testing out the new app. Expect a lot of frustration if they do not make any changes.