while i do not have a mac, and use DAS models myself, i think it probably depends on what your main goals are… (which you have outlined in your linked post)
im not sure how time machine works with multiple devices, if they all need to be backed up onto the 1 single drobo, but as the drobo-s is a legacy model (and i still have one myself on windows), the 5N seems to come with osx support for time machine, and also can cater for 64TB max volumes, as mentioned here, and might be a better fit: http://www.drobo.com/storage-products/5n/
please hang in there a bit as there are several mac users of both das and nas drobos who might be able to share their setup or tips for you
I contacted an Apple Support person and they seem to think the AppleTV and AirPort Extreme can be connected to the Drobo 5N and Drobo S.
He reckons the AppleTV will access the iTunes library that’s on the 5N, which is news to me.
I’d want to use the 5N as a bit of a media server or a personal cloud and the Drobo S as a backup drive I suppose.
The “S” would be connected to the Air Port Extreme’s USB and the AppleTV connected to the 5N… I think.
(Last night the Drobo S went bananas again after I inserted a larger drive at its suggestion. I replaced a 2TB with a 4TB drive and the Drobo reckons is only 3TB in size so I removed it and put the 2TB back in. The Drobo S was in rebuild mode when I left home this morning. I’m having the 4TB looked at this afternoon to see if it’s faulty.)