Have quite a few hours on the -400. It went very well, but the hardest part was doing a hot start. If you did not get it going in the first one or two tries, you were in for a wait as the next try or two would suck the battery dry! (ground power was always a good option and some cables in the boot would be a good idea)
Flinders Island Airways had one back in the 60's and 70's (VH-FOE) and it did the paper run from MB to Mildura with the Herald every week day. MIA was the only place it shut down for fuel. The other stops the engine was left running.
I did some IFR training in one with the owner back in the 70's and I recall it was quite a handful for someone with limited experience. Not a lot of room for maps etc., so you had to plan your trip and the placement of the charts etc very well.
Handling wise it was good, but the effect of the large engine was always there during the flare. Cant remember the fuel burn, but recall somewhere between 15 and 18 gph in those days (??).