Its tested against many of the test-vectors (key varying, plaintext varying, Monte Carlo), which is the only contract it needs to fulfil... I've some speed/timing information now:
128 bit, key setup 0.37ms
128 bit, ECB, encryption 0.58ms / block (27.5kB/s)
128 bit, ECB, decryption 0.77ms / block (20.5kB/s)
192 bit, key setup 0.41ms
192 bit, ECB, encryption 0.71ms / block (22.5kB/s)
192 bit, ECB, decryption 0.92ms / block (17.5kB/s)
256 bit, key setup 0.52ms
256 bit, ECB, encryption 0.82ms / block (19.5kB/s)
256 bit, ECB, decryption 1.09ms / block (14.5kB/s)
(CBC modes are a little slower than ECB)
(All ATmega328p, 16MHz)