frankv:dwl: Another first happening as I write this
See http://www.avweb.com/eletter/archives/101/3097-full.html?ET=avweb:e3097:220868a:&st=email#224415 -- the first electric-powered aircraft to cross the Channel was the Solar Challenger, 34 years ago.
Good point and those earlier flights were amazing, especially pedal powered. I think there is a difference between initial concepts which were quite fragile and needed good conditions (as does Solar Impulse) and prototypes which perform similar to their petrol counterparts and can cope with a range of conditions.
The definition of what means first is definitely in question although Airbus has been more specific than the headlines (which I agree are wrong) with the current wording on their website of "Airbus Group’s E-Fan technology demonstrator has become the world’s first twin-engine electric plane taking off with its own power to successfully cross the English Channel". This puts the Cri-Cri need to piggy back and not taking off into different category (it was twin engine!).
The resilience and practicality of those concept aircraft is well below electric production aircraft like the Pipistrel. Sad to see Solar Impulse with battery problems - from website news "Si2 has suffered battery damages due to overheating. The damage to certain parts of the batteries is irreversible and will require repairs and replacements that will take several weeks to work through." They put a lot of effort into insulating the batteries to produce power at low temperatures which probably didn't help (massive challenge with altitude range).
I think we have reach the point where electric cars are quite viable now and if fuel and maintenance costs included starting to get parity with fossil fuels. For aircraft a bit further to go.