I can't stress the rubbishness of this. As Unicorn said, it doesn't have any cool sound effects, just voices, or rather a voice, and it's not Optimus Prime's, or anyone elses! I have returned mine, it's really that bad! Plus, the phrases aren't up to much:

"I am Optimus Prime" (Hard to believe)
"We must protect the Allspark Cube"
"We must protect the Energon Cube" (we get the idea)
"Megatron is in my sights"
"We must stop the Decepticons"
"Autobots transform and rollout"

Generally, a little uninspiring, but all the more because the voice is all wrong. Give it a miss if you're a die-hard Transformer fan, it'll only disappoint you.

This is not small it really bulks up your pocket so not the best thing to have on your keys.
Next the sounds, I was expecting sounds of the transformers transforming etc but you get none of that instead just one characters voice on all buttons.