When i first did it (before I was on it for maintenance...you could see where that went lol) but I had already been doing opiates for a while, my tolerance was fairly established~300mg morphine, .4 smoked tar of good quality etc, and I took about 2mg sublingual.
I was solidly high/euphoric/socially lubricated for a GOOD 16hours, after that, I felt residual effects for the next 12 hours or so.
I could take 2-4mg sublingually and get the same results consistently when I took it like once a week, rush wasn't present but you would just start feeling it slowly, not as good as oxy or a full agonist, but still a great high with good opiate effects, IMO better than tramadol/codeine.
When I began snorting I found a much better rush and would only need to do 2mg at the most to get a solid rush, with that ROA i would rate it ALMOST as good as something like hydro because of its ease of ingestion and duration of high, and the high itself because it was very easy to make it go unnoticed, yet it was still present and enjoyable.
The best "light" intoxication I've experienced, if that makes sense, higher doses are not linearly better like pretty much every other drug (other than some weird shit like gabapentin or something), so taking more definitely does not mean it will be better, getting your dosage on point with your tolerance is very important, not just for safety either.
Everyone needs to remember that those with moderate tolerances trying bupe out should NOT use the standard pill dosage of 8mg, even if you have a high tolerance, still, you should start with something like 1-2mg and go from there. Bupe is unique in another way in that taking small amounts over a period of time (when not IV'ing) does NOT effect perception of the high or "rush" because of it's incredibly long duration. This should also carry over into another piece of advice in which the user should always be extra careful when redosing by taking into account this time period.
My recreation exp. with bupe-