My two bits.
Rollers worked great in my 200S. Same weight killed the flat spot, but didn't do much for top end.
Still they were a definite improvement from the rollers.
I run the OEM rollers in my SYM since reports are that Dr. Pulley's work fine, but there's no gain. SYM built the HD to be a bit more performance oriented than the Kymcos in the same class so what gain there was seems to already be there.
My Burgman 650 doesn't use 'em so no opinion there.
Some folks report issues of 'em doing all kinds of interesting stuff. For instance there are more than a couple reports of them flipping in Burgman 400s. Usually not right away.
Others, like xsel report they didn't work well at all, & I know of at least one that they come in stock. (BV350).
So it varies by bike. I suspect if you have a bike they didn't like you'd do better with 'em if you replaced your OEM setup with all Dr. Pulley stuff that's likely engineered with sliders in mind.