It's a great thing: Small, with many options, cleverly designed.
A big plus is the ability to use a midi pedal (MWave Chocolate Plus),
so you don't have to be limited to one button.
Another huge plus is the ability to use NAM models.
In my opinion, this makes the GP-5 an unbeatable choice.
What I'm a little disappointed with so far is the sound: I've also tried the NAM models. It's not bad, but still, if you're used to a tube sound, it's not quite "it". Maybe that's right. I'll try to look into it further and change my comment if necessary. So far, however, the many enthusiastic comments seem more like "hype" than accurate reality.
Still: For this price with so many features and quality workmanship, a great idea and a great thing.