> - would waiting to print the receipt at the end cause a big slowdown vs printing as you ring items up? (I believe with most current systems, items can be added and removed, and they show up as 'add' and 'remove' line items, because it does print as you scan.)

Most (all?) stores I go to print the receipt at the end of checkout, and it takes maybe 3 seconds at most, so I don't think that's an issue.

I would also be concerned that the longer receipt length means that people will be less likely to actually read it. (I know I personally tend to gloss over really long/verbose receipts, but I take the time to look at ones that are more densely packed. Maybe that's just me though.)