I was waiting for adequate data and information before posting. Believe it or not, I have replaced Guhl's ECU Flash with Steve's (Shooudaben) Mountain Runner ECU Flash. Have been using it for over two months now and over 1,000 miles. I was hoping it would be longer before posting, but the riding season is well past and so the miles come slowly now
Keep in mind it has been many years since I have ridden with the stock ECU, so my observations are mostly to contrast and compare the two re-flashes. The most striking difference with Shoodaben is the ease of shifting- both up and down, both clutchfull and clutchless. I am not exactly sure the theory about how this is possible with a flash. But it is real and impressive, and seems to hold through all gears (of course, it is MOST noticeable in lower gears) and most all situations. I also believe the Shoodaben flash also has a better tolerance of lower RPM in higher gears.
Throttle control at lower RPM/speed is also easier. I can verify it is probably not necessary to have a "Throttle Tamer" (G2 Street Tamer Throttle Tube) when you have the Shoodaben flash.... but since I do have one and I don't want to remove it (it is a nice metal tube that is so much nicer to use than the stock plastic one). If you have both the Shoodaben flash AND the Throttle Tamer, the "taming" is a little overdone (something I feared a bit, but as it turns out, it isn't so overdone that it is a problem.... at least not for me, just takes a bit a practice).
Performance wise, I notice no difference. But I didn't expect to, either. Both are strong and fast and eliminate the horrible stock lag and weak spots; the huge difference over stock are present on both flashes. I would characterize the Guhl as more twitchy and hyper, and the Shoodaben as more refined and reasonable.
I logged exact fuel mileage over many tanks, before and after the reflash. I do not notice any statistically significant difference in fuel economy between the two. Both are an improvement over stock by a few MPG.
Overall, I think the Shoodaben flash is much better, especially for the 99% of riding most of us do. The bike is smoother, more predictable, more comfortable, and more enjoyable to ride. I greatly enjoyed interacting with Steve. He is professional, competent, prompt, more than willing to answer any questions, and cares about customer satisfaction very much. He put a lot of time and refining effort into the product, and it shows.