Well, this depends. Personally, I have extremely rarely experienced any severe system problems, because I allow my Mint systems to install all updates as Ubuntu would do. I.e. All 5 security levels are marked "visible" and "safe" for installation here.
In Janaury 2013 a bug affected kernels 3.2.0-36 and 3.5.0-22. It was fixed two kernel updates later. This was the only regression which affected my systems like any system using the 2 kernels. - Yet, other users may have had different experiences. There is no warranty.
On the one hand, level 4 and 5 updates are supposed to fix bugs which affect really low level software, kernel and hardware drivers. On the other hand it is possible that what fixes a problem for one user will create a different problem for another user.
To be honest:
I hardly ever allow kernel updates to be performed the same day the new kernel has been released. I tend to wait for about a week monitoring the Mint and the Ubuntu forums for bug reports related to the current kernel update.
Enlightened by Lucid Lynx, enchanted by Maya, impressed by Petra.