I agree Paddy. I don't know if it actually tastes any different, but it is preferable to drink from glass for some odd reason. The test would be to have identical beer in different containers poured into a glass by somebody else to see if they can be distinguished in a blind taste test. Say VB for example, out of a bottle and a can. Once it's poured into a glass can you tell which is which?
I very rarely drink home brew directly from a PET, or even a glass bottle really, although I have done and by the end of it, you're really not enjoying it too much. Whereas if you pour into a jug or several glasses it's all fine but that's because of the yeast sediment being stirred up. I find the same thing with Coopers Pale Ale as its bottle conditioned.
When I bottle my next 2 buckets either today or tomorrow, I'll do a little test with some in glass and some in PET to see if it makes any difference out of the same fermenter. I'll get my wife to pour me a glass out of each and see if I can taste any difference.