6 years later I hardly ever plug in my laptop - its wifi all the way. No ARM based tablets that I know of have an ethernet port, and I don't see anyone complaining about it.
Note: I'm using an 802.11ac router and a laptop with a Centrino 6300 chipset. I have the 5Ghz spectrum all to myself. For bulk transfers I get consistent speeds of close to 100Mbit.
For daily stuff, sure. When I need to shift gigs and gigs of media or VMs or whatever though: Cabled is the only way.
It's the only thing which is reliable enough to not make me tear my hair out and for stuff like this performance really matters. Especially when it's orders of magnitude faster. To some people, not having a physical ethernet port seriously is a deal-killer. Yes.
Apple has successfully shipped models without it, but Apple's biggest market-segment isn't IT professionals. It's non-technical people fed up with Windows and hipster bloggers.
I use an old macbook (that has an ethernet port). When it comes time to replace it I'll buy a dongle with the new one, and on the relatively rare cases I actually need it use that. I can't really imagine it ever being a significant issue to me.