Ring of Freedom of Movement Price...

[two]

rendering oneself immune to [Death] descriptor and negative energy attacks makes undead a joke?

Here I thought it simply got rid of a horrible part of the game A good deal of undead dont even use negative levels anyway, is there some part of the spell I am missing?

No, just that a lot of the undead that PC's hate fighting the most do a lot of negative energy stuff. It does not make all undead a joke; but it makes them infinitely less scary to fight.

Plus, you'll never drop deap because of a [Death] descriptor effect. Which can't hurt!