Monday Mutant 4: Process of Illumination (cipher)

Monday Mutants is a series in which I will attempt to experiment with "mutant" puzzles. These could be existing puzzle types with an unusual change in the rules, hybrids combining elements from multiple puzzle types, or puzzle types neither invented nor popularized by Nikoli.
In this Process of Illumination puzzle, the given numbers have been replaced by letters; all instances of a particular letter represent the same number, but two different letters must represent different numbers. The rules are otherwise unchanged.
Two Monday Mutants this week? Really? Yes. Expect more weeks like this whenever I feel that it is appropriate. :)