I tried SC because I needed a caddy but a simple one. SC is exactly that. It is simple in functionality and simple in use. You create some products, and then you create an article with plugin codes referring to those products - and there is a module to show what is in the cart. There is no functionality to add charges or taxes, so I suggested that as a new feature. The layout is not great but good enough. Multi-lingual support is built in but few languages are packaged. I had no problems with bugs. All in all SC is exactly what the name says and what I needed.

Jonathan is very friendly and on the ball, and that shows in this extension. Attachments is one of the most user-friendly extensions I have seen and it provides a very simple but effective way to offering downloads.

I wanted to put some downloads on my site but did not want to put visitors through the motions of clicking through sections, categories and lists to end up wondering what the details really mean, as is the case on many Joomla sites with downloads. With attachments I can simply create an article, write something relevant about the download, and attach the download to the article. Convenient for me, and convenient for my visitors!

I would have rated this as excellent if there as a way to update an attached file, to select show or hide on section and category level, and to force downloaders to accept some terms first. I have hacked these features into my installation and I hope and expect that one of the next versions will merrit the full five stars.

Attachments might be too straightforward for commercial websites making money off downloads, but I warmly recommend it for other uses, including especially for other extension developers wanting to offer their extensions as downloads.

What I was looking for was simply a system to have articles rated and commented upon. mXcomment does that and much more (see the list of features), including keywords which can be used as tags and related items based on those. All in all mXcomment goes a long way to get from an amateur static site to an interactive professional site, and this without requiring any knowledge or understanding beyond knowing how to get around in the Joomla back-end. I am new to Joomla so don't rely on me for expert advice, but I can tell novices like myself that using mXcomment is really easy.
There are three things that would have made me deduct a star if the component had not been free (but then again, it is free!). 1) I really would have liked a tag cloud to go with the keywords functionality. 2) I don't like the word "favoured" very much, which is used for 'favourites'. 3) I had some trouble with the content pane spilling over on pages with two content columns (such as the blog and news section) plus right and left columns, but that depends on the sizing of the main template layout and the display. Anyway, I managed to solve it by playing with the templates and in doing so I found out that the author is well-willing and supportive.
I have not tried mXcomment's competition, but having mXcomment I really don't have any need to try anything else!