He works too slowly(for me)to be much use to me.
Can (for me)It be omitted, (I think It can be omitted because "to me" give that information.
He works too slowly(for me)to be much use to me.
Can (for me)It be omitted, (I think It can be omitted because "to me" give that information.
He works too slowly (for me) to be [of] much use to me.
I have added of.
The preposition phrase for me should be omitted:
He works too slowly to be of much use to me.
Having for me could be possible in a situation where you have a worker serving several supervisors. This worker is not always slow; he is slow only when he is doing your projects. Your example could be read as
[He works too slowly for me] to be of much use to me.
The other supervisors can have him.
Even in such a situation, we should still omit that preposition phrase, to make the sentence less clumsy and avoid having it read as
[He works too slowly] [for me to be of much use to me].