How efficient is DSP builder ?

I prefer to think about possible solutions before using the tool. It may be possible use simple concatenated filters based on shift and adds or subtracts to implement what you want, especially if you have some freedom of choice in what is acceptable ripple or cutoff.

Nothing replaces a little bit of thought up front, but if the solution is not apparently simple by all means resort to the tool and save yourself a lot of time.

Mind you, I still use assembler too; you can probably guess my age, its my birthday today.