Check out the size of that Tervigon.
Personally I love the new models. However it creates an issue for tournament players everywhere if there is a significant size difference in their model compared to the official one. While the new ones have had me considering to finally making a tyranid army, the players that have been playing them for the last couple years......... are crying foul. (At least several are). Tournament wise, a model cannot really be of a different size without being considered "modelling for an advantage".
I know that personally, if a model is of a different size, I tend to allow its play against me, however many would not. When I play, I just generally agree with the player that we accept the scale of their model to be what the official one is, regardless of its real scale. This can be difficult, but its all you have, and in this case it makes it a very difficult since there was no model for so long. Think of all the money going into peoples armies that custom built all these tervigons.
Personally if they were my models, I would have the blades out, cutting and re-designing them to fit the new scale. Not having a model is one of the big drawbacks of some units, and part of the reasons (at least for me), not starting certain armies. For example, I really want a Voidraven or two in my Dark Eldar army...... Cant, I have no real good reference as to the scale of a conversion, and hence it is one of the things bugging me about dark eldar at the moment. An unusable unit in the Arsenal of an army is rough.
So we come down to this. What are tyranid players going to be doing now? Technically their conversions are not board legal in a tournament. Lots of tyranid players are initially upset. I still really love the models, love the release, but I can feel the tyranid players pains that are going through this.