The only problem with Ti rings is that if you run into an accident where the ring needs to be cut off it’s almost impossible for standard hospital equipment to do it.
A more practical problem with alternative materials is that they can't be resized (some jewelers will resize Ti a little, but it's challenging). The alternative materials are cheap enough that you can buy a replacement that's the right size, but if you're sentimental (and a wedding band seems like something one might be sentimental about) it's a problem.
There's nothing wrong with alternative materials, it's just that sometimes the drawbacks are overlooked while being dazzled by the advantages.
Cutting Stainless, Titanium rings: http://www.loupe-magnifier.com/electric-ring-cutter.htm
Cracking Tungsten rings : http://www.loupe-magnifier.com/tungsten_finger_ring_removal_...
UCSF Fresno PDF on "Emergency Hard Metal Ring Removal" http://www.loupe-magnifier.com/snowdenposter2010.pdf