How efficient is DSP builder ?

I am more impressed with the Synplify DSP product than I am with the Altera DSP product. Altera is coming out with an Advanced blockset that will allow you to do multi-rate filters.

In general, if you are happy with what a megafunction will give to you - then that is exactly what Altera builds. If you need more than that - coding by hand is the way to go.

Personally, I've coded everything by hand that ends up in a product. I am interested in the "import HDL" option in the Altera DSP blocks to perform accelerated simulations on a target platform, but it croaked on my HDL that was synthesizable in Quartus II.