I once attended a casting demonstration by Ed Jaworowski and was enormously impressed. I have spoken with him several times since at the TFO booth at the Somerset Show, cheek and jowl to our PHWFF booth (provided to us by TFO). A disciple and close friend of Lefty's he is an important force behind TFO's rods. I respect his opinions and look forward to reading his fly line article.
On our Forum, I often write about fly line design and selection which, along with leaders, I consider the crucial performance defining component of a fly outfit. Because RIO (yes, a little inconsistently) posts diagrams and grain weights on their site, SA and Cortland have followed. The arguably obsolete AFTMA system does provide an interpretable base line reference applicable to all lines despite widely varying head lengths, taper designs and departure, sometimes radicle, from the 30' standards. I keep their chart in the Tackle Data folder on my computer for frequent reference. I would not suggest it is intuitive but having a taper diagram and 30' grain weight of an unfamiliar fly line offers usable data about what one might expect from the lines ability to load a given rod. Of course, there is no substitute for actually casting the line on the rod in question and this, more than the diversity of variation among modern lines, is the dilemma. We can easily go to a shop or show and cast a rod but various lines?, much harder. And I'm not even talking about the impact of differing coatings, cores, stiffness/suppleness, surface embossing and importantly, weight distribution. I am no minimalist and I embrace the breadth of choices and fish lines from all the major manufacturers, RIO, SA, Airflo and Cortland. The new line I embraced into my kit this past season was Cortland's "true weight" Omni-Verse, perfect on my SKY#5 like IT Gold is just right for my NRX#5 and SA's MEDT is Sage ONE's favorite...I often select one of these 9'/#5's over the other based on the line as well as the very different personalities of each of these fine rods.
When I got ONE some 6 years ago now, I tried several lines on it and settled on RIO Gold (which happens to conform to Sage's recommendation). I tried RIO Grand on it, which is really 6-weight line marked as a 5, it was dulling horrible. I tried Airflo Tactical and Rangefinder, blah and bad but I thought Gold was great. It is a great line and ONE liked it fine but then my pard, Dillon, put a MEDT on his ONE, I tried it and it sang a sharper tune...so I happily switched too and this seminal innovative line design in true AFTMA weight rendered this great rod greater still. Herein is a methodology to experimenting with different lines without buying a bushel basket of them like I have. Get together in a park with a group of friends of club members with all your favorite 5-weight outfits and cast one another's rods and then switch reels with various line around. I have performed this fun experiment a bunch of times, usually on hot, no hatch afternoons in Craig, Montana when a number of my fishing buddies are in town, and we always learn a lot. Sometimes about a better matching line for our preferred rod as is the intent and regrettably sometimes one of us says, "hmm, I think I bought the wrong rod, I like this one much better".