I used these for the first time yesterday, on a day trip from Norwich to Felixstowe via Ipswich. The outward journey was on a 745/0, the return on a 745/1, and they ran perfectly to time, as did the 755/3 on the Felixstowe branch. I like them very much, though the outsides were rather grubby - they could do with a wash more frequently. A serious point is that to get out of some of the seating bays into the cetral aisle requires stepping down, which is easy to miss - perhaps a warning sign on those seats would help?
A question - how will seat reservations work on services operated by the 745/1s which do not have the carriages labelled as the 745/0s do?