I used a G2 for a year and it was the most unreliable piece of gear I've ever owned. I might have had a lemon, but the fact remains that it crapped out on me twice at shows and I finally pulled it out of my rack and sent it back to Lexicon (for the third time) and told them they could keep it. They then called me to say they had fixed it for good and were awaiting my credit card number to charge ME for shipping it back. I told them I didn't care to get it back badly enough to spend the $70 bucks, so they now tell me they'll send it out when they get the chance. It sounded fantastic when it worked but I would rather have no effects at all then go through that nightmare again. Again, this is just my personal experience.
Another thing to consider is how many MPX G2s you see for sale on ebay. When I was considering selling mine, I kept track of what other people were getting for their G2s. At one point, there were six for sale and only one ended up selling for what the person was asking for (about $800). On the other hand, you rarely see any TC Electronics G-majors or G-Forces on ebay. I think that tells you something about most people's experiences with these units.