I was talking about a number of sites all over the web (including several at Google) that user agent string sniff and tell opera that it isn't supported, not maps specifically.

But, speaking of maps specifically, maps.google.com in desktop Opera works fine, but clearly you didn't try using Opera Mobile, because as soon as you start dragging the map, it disappears.

(at least on a galaxy nexus running jelly bean)

Another example that I encounter semi-regularly is Google Groups. It does user-agent sniffing to block Firefox with Javascript disabled. Change the ua to something random and it works fine without javascript.

Maps on Opera mobile works (Nexus4). It just lags like nobody's business.