I have tried a few others shopping cart extensions on here, probably all the major ones except Virtuemart and I have to say hands down Mijoshop is the best, and it has been an absolute pleasure configuring it and working with it and receiving amazing support from the team.
Combining Opencart and Joomla makes absolute sense to me, Opencart is the Joomla equivalent in the shopping cart world, with all the benefits like a big community, lots of extensions not to mention its free!
Mijoshop is easy to set up and use, with an uncluttered and intuitive backend yet is so advanced and powerful at the same time. It's import and migration system works very well, it looks great out of the box especially in Yootheme templates which is what I used for it (see here if you like vikingmobilityaids dot com)
It is easy to style, change wording etc and button css class can be changed from options (very sweet)
They are releasing a responsive version this week I have been told which I am very excited about.
The support has been outstanding, friendly and very helpful with Yuluf helping me to configure my spreadsheet for 1800 products! I'm sure he spent a few hours on it.
All in all I am excited to have found an E-Commerce component for Joomla that works so well and ticks all the boxes. Give it a try you won't regret it.