The points in that post are valid. You will see some space reduction from turning on design/data compression, but how much you will see depends on the composition of your databases. Databases with more design elements will see more benefit from design compression. Since data compression only works on rich text data, not plain text or attachments, the improvement you will see depends on whether your databases have lots of rich text. (If you have lots of attachments, you should also be using DAOS and LZ1 compression.)
It is also true that you will incur some performance overhead doing compression and decompression, but it's something of a tradeoff- more CPU usage for less I/O traffic. Since many Domino servers are more I/O-bound than CPU-bound, this could indeed be a worthwhile tradeoff for you.
The only way to know how much space you will save or performance impact you will see in your environment is to test it, carefully measuring the results against your current performance baseline. Hopefully you are already capturing Domino statistics related to CPU, memory, disk and network usage- if not, do so for a few months to get a feeling for how your server performs and then turn on one compression feature at a time to see what impact you get.