So I got the photos back today. The service is pretty quick; I sent the order at 16:45, and had a ready-for-collection confirmation at 10:41 the next day. After braving the lines at Costco (no fun), I had a look at them.
The prints are pretty good; colour’s bright, everything’s sharp, and there’s no obvious digital artefacts. But I got a bunch of dupes (maybe those failed uploads didn’t really fail at all). If I needed pictures again in a hurry and cheaply, I might go for Costco, as long as it wasn’t for anything really important.
I’ll still thinking about a networkable photo-printer, though. CompuSmart had a demo HP Photosmart 8450 for cheap, but it had no cables or PSU, so was pretty useless.