I had one last Friday night. UA1034 SNA-SFO listed as 737-300 showed up as a -500. I was originally in 3A, but thought I'd switch to another seat so I can put one of my bags under the seat infront of me - full flight. The kind agent put me in 10F, exit row, economy plus. When the plane pulled into the gate, I recognized it was a -500 from its registration N902UA, didn't give it a 2nd thought. 10F on the 735 is one row BEHIND exit, and first row outside of E+. I pouted as I slumped into the seat with no channel 9 ATC. The cabin was chaotic as expected, and a gate agent approached as asked if I'd mind moving to row 1...