Well, I tipped over the edge no thanks to this thread. Stopped by my local JD dealer and they had a couple 380s on the showroom floor. There was a $300 rebate, plus another $150 test drive coupon, plus they knocked another $250 off as part of a garden-show promo they are running this weekend. At $700 off, I thought it was a good time to buy -- enough incentive to make up my mind. Got the 48" deck. They were going to throw in free delivery too, but I would have had to wait until next week, so I offered to transport home myself. Will pickup tomorrow morning.
Now I need to figure out what to do with my old LT-150. It would cost $500 for a new deck shell, and probably another $75-150 for any rusted parts that can't be salvaged to transfer over to the new deck shell. I just didn't want to throw that much into a 15 year old mower that's only worth about $400-500. I may keep it around for oddball jobs or see if I can sell it to someone who doesn't need it for mowing or wants it for parts.