Good pedal but with only 3 seconds of sampling I would replace it with an effect with a much longer sample time. 3 seconds may have been quite an achievement in the mid 1980s when it was manufactured.
Well the GW50 is an effect Pedal, so all the effects aren't really good, but it'll do just fine for little gigs or just playing at home.
Although the Magicstomp performs complex functions internally, Yamaha has succeeded in keeping the user interface simple and easy to use. The real 'magic' here is that they've created a product so powerful and fun, it will be impossible for guitar players to resist.