In my opinion, there is no other finishing technique as completely satisfying as using the mattress stitch to sew a vertical seam between two pieces of stockinette stitch.
It's simple, straightforward, and leaves you with a clean, practically invisible join.
Perhaps the best part is that the mattress stitch is very easy to learn. If you haven't already mastered it, I highly recommend that you take some time to practice. You'll find yourself using it over and over again.
Watch this new how-to video provided by Berroco for a demonstration: