Rhino r4fxo with asterisk - how good are they?

Hi,

Just wanted to know if rhino cards specifically the r4fxo model type would be a good investment with asterisk and how good is their performance (specially those with echo cancellation). Anyone implemented rhino cards on their asterisk setup? can you site some advantages or disadvantages on using these cards and what should be watch for when having these cards with asterisk.

thank you.