I've got a bathroom sink that has flow that is faster than I would like when the faucet valves are full open. I know I could go get an low-flow aerator to slow the flow but right now I have just adjusted the wall stop valves to throttle the flow to what I want. This seems to work fine. Is there any problem with this as a long term solution?
As long as the static water pressure going to the stop valve is 60 PSI or less and the pipes are copper or galvanized, shutting the valve partly is fine.
If you find the water pressure is over the safe limit it would be wise to install a pressure reducing valve somewhere in-line with the houses' water supply line. Reducing valves allow you to adjust un-dually high water pressure to a safe setting.
Too high water pressure can rupture copper pipes, damage seals in faucets, and crack irrigation valves.