Anyone considering this Gen2 upgrade from Gen1 or doing the internals on their OE Gen2 rear shock should not rule it out. If you have to have Ohlin's Penski or don't mind parting with a grand or more for a rear shock then by all means have at it. If on a budget you can build or have built a comparable unit (valves, proper shims, oil etc.) for the street, Drag Strip if you buy a higher rated spring as Gordon 24 is doing, track day still an upgrade but with out the 30 some levels of adjustability of remote reservoir big $ shock. This is just my opinion concerning the needs of most riders & keep in mind I am not a professional builder but there is no black arts going on . Those seeking a specific specialized or the highest levels of riding/performance have to pony up and take the other route.
I completely agree that you can have a safe bike that performs extremely well with a properly setup or modified stock suspension system. Few of us can out ride even a box stock Busa rolled right off the showroom floor. Obviously the extreme power guys are taking the Busa to new levels but for us parts worshipers its a much more subtle elevation of the basic bike's personality.
That said, there is clearly a refinement to be had with expensive parts but the cost vs. benefit ratio can be difficult to justify for some. If you spend some time with an expensive refined bike like my BMW, it is clearly a level of refinement above the Busa. Yet the Busa is more compelling and fun to ride, and certainly my first choice saddle.
As it turns out the Busa is an engine, that's all that matters. And this formula has sustained it in a class of it's own for 20 years. Other bikes have evolved, the Busa is still an engine and you cannot deny Suzuki got it right in both concept and execution. Still, no matter what you bolt to it (even with Ti bolts, Lol) it's not going to turn with a literbike. If you taught that literbike jockey a lesson in the twisties, you beat the rider, not the bike. Frankly, the only real performance increase you can make to the Busa is, in my opinion, safer brakes and even more power.
My experiment is basically to see if I can give the Busa a feeling of more refinement. I have attempted to give the bike higher quality parts in all the places the rider interacts with the bike (suspension, brakes, controls). We will soon see if this transforms the bike into a "new thing" or an engine with expensive brakes!