UK perspective only:
My controller friends tell me that
sometimes a visual approach does help increase flow. On the other hand they rightly remark that asking for a visual approach when it is blatantly obvious you are being vectored around a pattern with half a dozen others in front is irritating and highly unlikely to be honoured.
However, merely stating that one is "visual" doesn't tell the controller what you want! This could lead to misunderstandings from both participants. Visual with what? Do you want to continue with the vectors / non-precision procedure / ILS or are you saying you can see the other traffic around you?
The correct transmission is "request visual approach", (a VISUAL APPROACH is a recognised definition), and now the controller knows in no uncertain terms that you wish to continue the approach with your own navigational visual reference rather than that of an instrument procedure, but he still has the duty of providing IFR separation around you (NB a "
Visual Approach" is not VFR; you haven't cancelled your IFR flight plan.)
1985 - your reference to those who ask you to "maintain high speed" is indeed annoying. Until when? What about our FL100 250kts restriction outwith Class A airspace? Am I going to cock up the controller's plan if he assumes I am going to keep 320kts all the way in and I can't? This is why, like you, I ask "what speed would you like?" which sometimes can sound unintentionally sarcastic but it's a valid question.
anotherthing - "pass your message" unfortunately seems to have been replaced by "ready to copy"
To digress, my local airport's approach frequency has started the unrequested rubbish of "Nobjet 123 this will be vectors to a visual approach for runway 36.." when there is a fully serviceable ILS radiating! To put pressure on a pilot to maneouvre visually in to an airport he is not familiar with is a right as far as I am aware that controllers don't have, and the request for visual approach should only be instigated by the pilot when he (and his colleague) are absolutely assured it will work safely. Discuss.....