What's being addressed there is a bug which, frankly, is overdue to be dealt with, and I'm glad they're doing so. Aside from that though...
Most people don't like vassals because their returns can be marginal. You whup somebody's ass and they capitulate... But then they have little in the way of resources to give you, won't trade tech, and are a liability for getting you into wars? horsehockey deal, it seems,a nd I believe this is why many people don't like them.
But that's not my experience. Vassals are a gamble, plain and simple, and if you dont' play your cards right, they will do you nothing but harm. You pick a vassal you had poor relations with before, or is of another religion, they probably won't trade much with you. If you bleed them dry, they will fall behind for tech and be no good in a war - and conversely if you let them go nuts, they won't be your vassals for long. To get a vassal to pay off, you need to keep them contained, happy, and advanced.
The advantages when you do? Well, it's easier to keep vassals happy and trading with you becuase of the vassal relationship - it gives a positive modifier. Other civs are less willing to go to war with someone with a vassal. Vassals add a lot of units to your wartime surplus that you don't have to pay for. Also, they are a seperate tech income from yours if you treat them right, since you can depend on them trading with you.
Vassals only pay off if you put a lot of work into them and plan them carefully. If you haphazardly pick them and then don't act in a manner to keep them happy, they will be a liability. Personally, I like this system - it's not a gimme, but the rewards are great, particularly if you want to go peaceful-builder'ish later in the game.