When switch rods first appeared, lots of media attention hyped up the rods' ability to cast with Spey and overhead techniques. To the casual rod buyer, that seemed to be the reason to buy a switch rod: you could cast where backcast room was limited, and also open up with a big double-haul where the bank allowed such casts. Nobody mentioned that most any two-handed rod will allow the same "switch" in casting style.
Then switch rods became the tool of choice for indicator fisherman, especially those switch rods with fast progressive tapers not unlike the most popular single-handed rods. The longer reach of the switch rod allowed better control and hook-setting abilities, and the extended handle allowed tight little stack mends to be sent a long way. Most guys I knew then were fishing double-taper lines two sizes bigger than the rod recommended, and they were covering water a long way out.
Meanwhile, the collective opinion of those anglers who swung flies exclusively seemed to be sliding toward a complete discounting of the switch rod. Guys I knew were talking about switch rods as all hype and no soul.
Personally, I've been swinging flies with switch rods going on ten years now, and they've become a staple of my quiver, more so every year. I've come to believe a switch rod is an essential tool for fishing small to medium-sized rivers, for fishing heavily wooded banks with overhanging limbs that don't allow clearance for a longer rod, and for fishing those high water days on bigger rivers when the swinging water shrinks to only a few feet off the bank.
What has allowed the switch rod to come into its own is part rod design and part line design.
More rod builders are moving away from the single-handed taper of so many of the early switch rods in lieu of a taper more like a two-handed rod. Naturally, the casting of switch rods has become effortless and graceful. Also, anglers have realized that by trimming down conventional Skagit heads to match the shorter rod, they can create a powerful pocket canon. Now Airflo is offering a Skagit head built for switch rods--which is an excellent head, by the way.
For those anglers hoping to swing weighted flies this winter, I recommend finding a switch rod that will cast a 450 grain or bigger Skagit head. If you want to throw some real heavy junk and a heavy tip, step up to a rod that throw a 550 grain head.
A long rod is a necessary tool, but it can be detriment on some runs and during some water conditions. A switch rod will allow you to reach fish you otherwise would have missed.