Most performant way of converting int to string

[Andrew Chapman via Digitalmars-d-learn]

Sorry if this is a silly question but is the to! method from the 
conv library the most efficient way of converting an integer 
value to a string?

e.g.
string s = to!string(100);
I'm seeing a pretty dramatic slow down in my code when I use a 
conversion like this (when looped over 10 million iterations for 
benchmarking).

Cheers!