Checkout software market research help required

I'm creating a new in-store checkout solution, which will include bitcoin . Obviously I have a good idea of what I think would make a good checkout and have cased a lot of the existing software packages, but this is software for customers, not for me, so I'm looking for existing checkout operators (or if you know any checkout operators) to answer the following simple questions in as much or as little detail as they feel is helpful.

What features of your current checkout software are particularly well implemented?

What irritates you about your current checkout? (can be non-software related)

What do you think could be added to your checkout that would make it easier to use?

I've asked a few people these questions and have some good info, please post responses here in case someone else is also looking into doing this so they can also create software that meets what customers actually want and not just what the devs think they want.

So far:
Fast response time.
If interrupted the previous info isn't lost and its easy to get back to.
Doesn't look ugly.

Thanks in advance for helping with market research.