I have run HOB Reef Octo Skimmer, and In sump models. I would recommend both. There are better skimmers out there, but most will cost a lot more than a Reef Octopus. IMO, you can't beat them for the price.
I did have some issues with the HOB BH1000 (this is an older model of the Classic 100 HOB you posted) model I ran... tuning it in is done by raising or lowering the collection cup. This is a bit of a PITA and I did get some leaking issues eventually. But when it was tuned in properly and running good, the thing pulled skimmate like a champ. Thick dark gross looking skimmate.