Having just finished an electric HERMS setup (Thanks Kal! Awesome website-theelecricbrewery.com) I can tell you with absolute certainty that the conveniences do not outweigh the costs. I did it because I had a habbit of tinkering with my equipment (hmmm hmmm hmmm, huh huh huh) between every brew and never dialed in the process. Efficiency, final volume, and FG would fluctuate every time I bought or made a new gadget. So I decided to give in to give in and do everything at once.
If the goal was simply consistent, quality beer, I probably would have just went with a nice burner, 10 gal pot, 10 gal cooler, counterflow chiller, and a spare propane tank. To make better beer, brewing more often probably will yeild much better results than tricking out your setup.
My guess is that most people that go RIMS/HERMS like tinkering and gadgets as much as they like brewing. If that's the case for you, then go for it. I'm really happy with mine.