idle at low will depend on many factors.
My SLC had shaved camshaft (cam lube rail cloged) and years-of-no-drive cloged injectors when I purchased her.
She could hardly idle at 700-800rpm in D. Idle in N was ~900-1000 or she stalls, jerks and jumps.
Nearly new camshafts (original 01/02, no visible marks of wear) and new set of injectors produced purring at 750rpm in N and smooth enough idle of 600-650 in D. After closing/replacing all vacuum leaks and replacing all hoses where fuel mixture passes, she can idle at ~400rpm and she copes with ease (just for test purpose).
And it feels much more powerfull. Way much more.
I believe my problems were most common (power killer) problems.