It's slow and it has to build the packages most of the time. pkgin will install a precompiled packages very quickly. It is also a whole C program and Homebrew is just ruby scripts.
And that's a problem?
I would argue that it's a feature. Due to Homebrew being written in Ruby, it has easily allowed over 4,000 contributors [1]. Recipes are easy to read and inspect for verification purposes.
What is the advantage of C over Ruby?
[1](https://github.com/Homebrew/homebrew/graphs/contributors)
At least, not using /usr/local myself, I see a lot of packages building because they have detected I changed the base directory.
Give it a try, you might like it (because it rocks!)
Why use OSX, then? Shouldn't you be using Gentoo?