In the days of Joomla 1.5 there were a few limitations to using core content for anything other than simple pages. Yes, plugins were available but they couldn’t handle things like nested categories, item specific galleries and videos etc etc. Many components were created to combat those limitations but the outright winner in terms of number of users and community is (by a longshot) k2.
Much of its functionality has now made it to the Joomla core (nested categories, tags, featured images) but it continues to be popular with its users (old and new). Sometimes it can be a bugger to configure, but once it’s set up you can have multiple templates with a very flexible output. For an example, take a look at Joomlabamboo’s responsive k2 template set ‘zenkit’.
Unfortunately there is one thing it lacks, and that is good spam prevention. The choices are recaptcha and stopforumspam. These days spammers get increasingly sophisticated in their methods and can get around most things quite easily. Just google ‘captcha bypass’ and look at the prices to see what I mean.
Anyway, I have seen some sites grind to a halt because of the number of spam comments submitted and today I was asked to look at one that was getting hit about once every ten minutes which when having to moderate can be pretty annoying.