1962 250 GTO and McLaren F1 LM (IIRC, BADNED said a while ago that this one had a tiny chance of appearing in FM5 so fingers crossed) are my most wanted cars.First DLC pack I've probably been super happy about. A nice mix of exotic new and old classics.
The Zagato, 312P and 850 are awesome.
Now where's the iconic '62 Ferrari GTO??
I know there are still and there will always be requests but I really feel that Turn 10 has been releasing killer packs for Forza 4 and they've managed to strike a great balance between highly requested cars (new or old), race cars, huge surprises (S1 for examples), funny surprises (Pinto and now the wagon) and just regular cars being added or renewed (Polo, Clio, etc...).
IMO Forza 3 had at least one or two packs that were really lacklusters (the one with the Jeep comes to mind) but Forza 4 has been on a roll regarding car selection for packs and I think I've always been interested in at least half of each pack so far. Seeing what's to come from FC's list, I can safely say that future DLCs will still have my interest.

If only they selected the tracks as well as the cars...