As a Meguiar's employee who got fairly well involved with Jason Rose while this system was being developed, perhaps I can assist a bit here with the "D301 perception" issue being discussed here.
What a lot of people tend to lose sight of is what this system was developed for: primarily it is a very fast, very safe two step system that allows high volume reconditioning facilities to move many vehicles through their system without having to train employees how to properly use a rotary buffer. For many of these places (think Manheim Auctions, for example) the required level of defect removal is fairly high, but the expectations for the level of finish demanded by a discerning detailer isn't there. They have fairly high operator turnover and can't afford to train everyone on rotary use, and they can't afford the potential damage that a total novice could cause with a rotary. So this system allows them to put quickly trained operators onto virtually any vehicle and safely remove the majority of defects very quickly, and then finish off with a very capable cleaner wax (D301) that will leave a finish superior to what they had been getting in the past. For the purposes of prepping the car for auction it is far, far beyond their expectations.
Now you guys step in and you're demanding a higher level of finish for an end result. You demand it, your customers demand it. That's fine. Heck, that's great even. And maybe you prefer the way M205 or 85rd finish down. Great. Maybe you prefer the final look or durability of NXT, Ultimate Wax, Blackfire, Pinnacle, Zaino, Collonite, etc etc etc. That's fine too.
There's no doubt that D300 on the cutting disc has practically revolutionized the way you guys approach many detailing projects, and the overwhelming positive feedback has been, well, overwhelming. Many of you have also found D301 on the finishing disc to be a great one step process on paint with light to moderate marring and which responds well to such an approach. Heck, maybe you're even then topping with something else. Cool.
But even in our own marketing information on the system we talk about using the cutting disc and D300 as the first step in a more thorough or critical detail, with M205 on a foam pad as the second step and M21 or other LSP to finish off.
For your own vehicles, if you're super critical, then maybe the three step with different products is the approach that works best for you. But if you're looking for a fast way to achieve a really nice finish with just two steps for a customer who's looking for a major improvement but isn't willing to pay you for 12 hours of work, D300/D301 can be hard to beat for overall speed vs results gained.