I'm a big fan of the 757-200 "16A and a pillow" segment, and have noticed my routes have moved from a 757-200 to a 757-300. So far, every segment has been EUA'ed, yet did notice on my first boarding that 14A/14B on the 757-300 appear to be centered to the 3-row-isle... meaning no pillow-and-a-bulkhead. I haven't sat in one yet, yet I don't look forward to it (prefer a bulkhead to rest against.).
Ditto on the "watch out for the equipment change". I once had the two-seat-row assigned on a -200 (up front, next to the lavs), and they moved it to a -300. Argh, as I was traveling with one other person.
Steve B.