Yes, I use Stanadyne performance additive on every tank. I've noticed easier starts and it seems to give a bit less smoke on startup, but that could be a placebo effect.
I use Archoil AR6500. I have Detroit Diesels with injectors with many tight fitting parts, so clean fuel with good lubricity is important. It has increased cetane for hotter, cleaner burning that gives about a 10% increase in mileage. Also dissolves sludge buildup in tanks and disperses water in the tank that helps Racor type filters remove the water. Cost is about 11¢/gallon.
AR6500 Diesel Treatment is the superior all-in-one diesel additive, developed to maximize engine performance. Increase diesel lubricity to protect your engine and improve fuel economy with a big cetane boost at every fill-up.
Links below to two-part article from Steve D'Antonio on fuel additives. Part 2 contains a lengthy quote from Bob Senter of Northern Lights on technical aspects of fuel lubricity which is enlightening (at least to me) and makes the case for additives in close-tolerance machinery such as Diesel Engines (just as Lepke notes). As an aside, it's helpful to cleave any conversation around additives into performance enhancement (lubricity) vs bug killers (biocides). The former is an ongoing maintenance program where as I view the latter (bugs) as an interdiction when needed. I do not prophylactically treat for biologics in fuel. I've run Stanadyne for years.