I used max from version 1.0 to 4.29. After I forced myself to learn Maya, I've never looked back. Maya may not be the most beautiful by it's looks but it is the most powerful and flexible 3d package I've ever seen. Here are few things that made me go "wow" while learning Maya:
- Nurbs (something that was a plague in max)
- Paint Effects
- Artisan
- 3D Paint tool
- UV editor (after learning how to use it properly)
- Particles
- Dynamics
- Trax Editor

One thing I really appreciate about Maya is that every function works (at least for me) exactly as I've expected. No funny stuff, bugs, weird behaviour or anything. It's just smooth as baby's skin

The most annoying thing while learning Maya was the camera navigation short cuts. Nowadays it's the opposite. If I'd had to work with Max again, it would be the same: pure pain in the... you know