I have a Polymer Stainless Gold Match that I use as my Bullseye gun. The chamber is unsupported, but I've never noticed my brass bulging at all. It does have the full-length guide rod, which the top shooters in my pistol league say is bad as I have to rotate the bushing on the barrel to take the gun down for cleaning; putting extra wear on that critical interface. (They just pull the take-down lever and take the slide off, then pull the short guide rod off the back of the recoil spring. Can't do that with a full length rod as there isn't enough clearance.)
How accurate is it - a lot more than I am.
The grip is great for me, I have large palms but short fingers. Never noticed the square front corners, that corner is just where my finger joint is and fits me fine. Do notice what passes for checkering on the front of the grip, I've slowly been smoothing it with some 400 grit sandpaper, just a few strokes at a time when I clean the gun. What I really like is the way the grip is relieved forward of the beavertail safety, it just fits my hand better than any other 1911 I've ever held.
The high capacity magazines are very expensive ($100+), and even the 10-rounders are over $30; and nothing else fits without modifying the magazine latch (Kimber does the modification and then the STI/Para-Ordinace double stack mags will work). The odd thing is that the magazine bases don't fit the bottom of the grip; there is extra plastic past the front of the grip, not enough on the sides; and the bases end at the back of the magazine tube leaving a big notch in the outline of the pistol.