What is Liferay?
Liferay is supposed to be the answer to your traditional corporate problems, such as: how can we store our documents in a shared, central repository that's easy to access direct from the desktop? And how can we have a central per-project calendar which everyone can easily sync with and update? All the stuff I'm pretty sure Sharepoint has solved (but don't get me started on that!).
We use Liferay and it was my misfortune to be the one who had to set it up and maintain it. There are a billion configuration options, the documentation is poor, there are so many different permissions and attributes on everything with so many ways they can interact I'd be amazed if there aren't massive security holes everywhere from my misconfiguring it all.
On top of that, the fundamentals we want to use it for never actually a) work well or b) work at all. For example, WebDAV is quite unreliable from various flavours of Windows - I'm sure that's Windows' fault, but most people (non-engineers) use that so it's a bit of a bummer.
As for missing features, the calendar portlet is next to useless with no sensible integration to people's own calendars or central iCal servers. The document library is next to useless with no ability to put commit comments next to a revision of a document and no way to control the version number for a given commit. Oh, and you can't recursively set permissions and the like on a folder and all its contents!
And yes we did raise all of these on the Liferay forums/bug trackers over the years but nothing ever changed.
Oh, and it's veeery slow, too. But that seems to be the norm for server-side stuff nowadays. Hey ho. So we keep using it and it keeps limping along but it's a shadow of what I was hoping it would be when I first read about it. Maybe it's all sunshine and rainbows in the latest Liferay but after going around the painful upgrade cycle a few times, I have no idea what the latest version is like.
I should temper all of this by saying I'm no sys admin and my company is too cheap to a) hire one and b) go for the commercial Liferay package. Still, let the downvotes roll in for one poor sod voicing his real world experience...