I'm so happy I discovered HikaShop. After failing miserably with a couple of other shopping cart extensions I was about ready to give up the whole idea in despair but luckily I decided to give HikaShop a go. The documentation could be better - in an ideal world there would be a simple, lynda.com-style video explaining how to get started - but the support forum was so helpful that I got myself sorted out fairly quickly. I'm using HikaShop Business edition with Falang for a multi-language shopping site and it was much easier to set up than I would have predicted. Tip to newcomers: following the setup on the Hikashop demo is a good way in, once you have an idea of the basics the documentation makes better sense.
So: good extension and excellent support - friendly, helpful, patient, seemingly always good-tempered - a pleasure to work with. I paid for the Business edition, partly for the extra features but also because I thought the developers deserve to get paid for their good work.