Agreed. That doesn't mean there aren't improvements to be made, but its pretty good.
As for improvements, one of the thing that really bugs me is the email itinerary function doesn't seem to work at all off the app (and I know off my wife's either - not sure why but given for both of us, I imagine we aren't the only ones). It used to - but not for the last few months. While we are on the email subject - I also never get purchase confirmations when booking on the app - only the e-ticket/receipt when that's issued. Not sure why.
Another thing I would love to see at some point is the ability to use TCVs when booking on the app.
These are a couple of little things of course. But generally works very well. Also like the ability to rebook on the app during IRROPS.