I think you see an uptick on quieter flights. I got double-upgraded on a couple of shorter weekend flights to/from DTW, for instance, but would probably only have been in C+ on at least one of them if I'd been silver. But otherwise, no, the main benefit is SP (for what that's worth) + the partner clubs internationally. You also do get SC club access for flights in F to/from Canada (and I think Mexico), which Silver doesn't get, but obviously the value of that depends on your travel patterns.