I have the Spark booster.
It's very versatile, and it sounds quite different depending on the mode you have set it on.
It's difficult to say what I like about it, but even in mid boost mode it's more transparent than a Tubescreamer.
I like that it works with several of my amps, where many boost pedals work well with one or the other amp. It's also cool to be able to change the mode playing with different types of guitars.
Anyway, I can highly recommend it. If it broke I would buy a new one straight away.