I've cast WF lines of different configuration on all of my rods since around the mid 80's. Recently I purchased an older Martin 67SS-A reel on ebay to fit on a beautiful old Browning 'Silaflex' 7' 6" 5/6wt, the reel had a new (old stock) S&A Aircell DT 6wt line. After attaching a leader I took my new rig to the lawn for a tryout, didn't expect much from the short, old glass rod and DT line........Boy was I in for a surprise, short/mid range cast were an absolute joy, and it was hardly any effort at all to toss nice tight loops 75'-85'. Not sure if it was the older glass rod, the line, or maybe the combination of the two, but I look forward to actively fishing with this rig in the future.
As soon as the chance comes to put the DT line on a good graphite rod like my Loomis IMX 8' 6" 6wt to play around with I will, and if the line performs equal too, or better than it did on the old Silaflex, I'll be adding a few DT lines to the arsenal. Dependent on the fishing situation, there certainly can be advantages to the use of a Double Taper.