Eric,
that is the same question I've been asking myself few months ago.
Finally, I decided to go with Maggie System 23. I got a new machine recently, but still didn't put it in service cause I didn't have time for that, due to a lot of work I had recently. I hope it will be ready in 2-3 weeks, and if you're not in a hurry, I'll come back here and report how it works once I try it.
But, from what I could see unpacking the machine it seems it's well built and it looks like it has enough "steel meat" to stay rigid and in tune, fences seems strong and all spindles rotate surprisingly easily when you rotate just one by your hand, which makes me believe that it's mechanics is good. I do not have experience with other brands of boring machines so it's not a real comparison against others, just my assessment of the machine in general.
Like many before me have said about using those machines - "Set and forget" is the way to go with this machines, and if you sometimes need a hole somewhere else than usual, maybe it's better just to use a piece of plywood to offset your working piece of the fence, instead of moving the fences around and dialing them all the time.
All the people from J & G Machinery I've been in contact with regarding the purchase gave been great to me, especially Andy from sales and Peter from technical support who answered all my technical questions (like how to connect that 3 phase machine through phase converter and some more).
Contrary to some other manufacturers (or their U.S. distributors) they had everything in stock and could ship it in 1-2 days.