Yup. In fact you should get it done after any work that involves disconnecting the suspension arms and suchlike.
Don't know about on a Mk4, but on a Mk3 There is some degree of adjustment available at the front for camber/tracking, but none at the back. Most alignment places will check the back anyway, but can't change anything.
I was pissed off with the last time I got mine done (ProTyre in Bristol). I specifically asked for the camber to be set on the lower tolerance (so I had a bit of negative camber, but not too much) and they didn't (in fact it was set closer to the upper tolerance), and I had a steering-wheel that was obviously not centered so they must have not clamped it. I would've had a whinge at them but I was last in and they were closing when I picked up the keys... so I've just resolved not to bother going to them again.
