I have Delrin bushings in my Duster, which is a street car despite being set up pretty aggressively for handling. I haven’t had any issues with running them on the street, they work great.
Now, as far as a noticeable improvement, it depends. When I installed the Delrin bushings I was replacing poly bushings. But they were installed with greaseable pivot pins, used with adjustable strut rods, and after 10k+ miles looked brand new after I wiped the grease off. I honestly didn’t notice a difference between the poly and Delrin bushings.
If your poly bushings weren’t installed or cared for properly you’ll see an improvement no matter what as long as you do the installation correctly. Both the poly and Delrin LCA bushings should be used with adjustable strut rods. The poly LCA bushings need greaseable pins. The Delrin LCA bushings are supposed to be self lubricating, so greaseable pins shouldn’t be necessary. Mine are installed with greaseable pins anyway though. Partly because I already had them, partly because they fit the Delrin bushings best of all the pins I had, and partly just as insurance in case I needed to grease them later.
If you intend to keep the factory strut rods, you should use rubber bushings at the LCA and the strut rod. A company called “Proforged” actually makes decent OE style LCA bushings. I can’t say how they hold up, but unlike the garbage Moog is putting out now they’re actually the right size and look decent. The strut rod bushings are an issue though. If you have the later, 73+ style strut rods the two piece bushings are not currently available and haven’t been for like a year. Moog has had massive issues supplying them, and at the moment no one else does. If you have the 67-72 style that uses the single piece strut rod bushing those are available.
There is a difference going from all OE rubber bushings and non-adjustable strut rods to either poly or Delrin bushings with adjustable strut rods. The handling and response is better and more accurate. The handling feels more precise, you don’t feel the slop and give that the OE stuff has. But keep in mind that’s not what you get changing a single bushing, that’s the result after changing everything. And keeping all the parts working together, ie, using the adjustable strut rods with the poly or Delrin bushings, tuning the length of the strut rods so there’s no binding, using modern alignment specs to match the level of performance of the tires being used, etc.