I just flew BOS-SLC-BOS and didn't have any trouble in either airport. I ended up with a LOT of time on my hands in the airport.

I flew out of Boston on 9/27 mid-morning. The check-in lines at DL were a little long but not terrible. No problem with security at all.
I flew out of SLC on Monday, mid-afternoon. The coach check-in line was quite long (maybe half hour?) but First Class/Medallion was very quick. Security can be quite a problem at SLC but there was no back-up there at all. I noticed they've added additional machines since I was there last.

Of course your mileage may vary!