The best benefit to Silver, in my opinion, is the E+ seating. This was obviously cut back as a benefit by changing it to T-24 hours only for silver, but I in general have not had trouble with getting it on my flight routes at least (domestic, ex-ORD). Priority security is nice as well, if you don't have it through your credit card. I think I've gotten one CPU since the merger--I used to get them once in a while before but that's essentially gone as a benefit to me.
About 75% of my travel is for work, and United is our "preferred" carrier, so it makes sense for me to stay struggling for Silver every year. I usually take United when traveling personally as well in order to get those EQM/EQS, if the price difference isn't substantial. All in all, it's a lot of little benefits that individually aren't much, but gives enough when combined to make traveling a bit more enjoyable.