I bought a G1 last Wednesday and so far, here's my thoughts on it:
Durability: If you like jumping on your pedals this may not be for you. In all fairness, the G1 is a lot sexier and a lot sturdier compared to its cousins the 505 and 505II. You have to watch out for the switches: although they seem tough enough, the fact that they are ABS plastic actuators with flimsy tact switches underneath may make you think twice before you do the 9-volt stomp on it.
Tip: use an adaptor. Somehow it bypasses the switching input jack so the unit stays on even without a cable plugged in.
Sounds: The unit offers a lot, leaving little to be desired. The distortion tones are varied, and you'll be hard-pressed to exhaust them all. The modulations are split into two modules so you can mix in some phase with the chorus, etc. Most of the modulation effects such as chorus, flange and pitch shift come in preset mixes, leaving the modulation speed fully adjustable. Sadly, this facility isn't available on tremolo and phaser effects on the COMP/EFX module, still the presets are pretty much usable. What I do miss are the extra EQ knobs for mid freq and presence. Plus the acoustic sim is a bit bland: I like the one on the G2 better.
Price: For the price of a brand-new Boss pedal you'd get a whole soiree of effects in a compact pedal. Novices saving their "baon" to buy gear will find the unit's functionality well worth the price. True, its plastic housing and somewhat limited flexibility may raise a few eyebrows, but for the rocker with an anemic wallet, it's a closed deal.