As is typical of forums, people will post about the issues they're having and not to let everyone know that everything is fine - otherwise the forums would no doubt be much larger than they are and the dullest of dull!
However, it's not that unusual for the mechatronic units to have issues (mine was replaced under warranty) and even out of warranty I've heard of exchange units being done for less than $2K or so?
It's also something that doesn't normally suffer a catastrophic failure but results in a rough driving experience with a jerky action. If you suspect something isn't right, the most common driving trait to show up any jerkiness is to reverse up a hill slowly eg backing out of an uphill driveway.
Another thing to bear in mind is that a DSG will never operate as smoothly as a normal automatic and can have some quirks. In saying that, I and a lot of others on here love it found it the best compromise between manual and a traditional auto to the point that future cars will be DSG only!
However if you're concerned that much about it then grab a manual, simple as that