An interesting point that no one has yet raised is whether Assange is extradite-able from the UK to the USA for espionage.
There is no question that a suspect can be extradited for ordinary criminal offences - i.e theft, rape, murder, fraud, assault, destroying property, etc.
However, most nations will not extradite for "political offences" - i.e offences which do not involve fundamental criminal law infringements as set out above and which are aimed at frustrating the government of the requesting country. For example, most nations will not extradite tax evaders.
The notion of "political offence" is codified for example in s. 46 of the Canadian Extradition Act. (see below).
I cannot conceive of a more blatantly "political offence" than espionage. If the UK intends to extradite Assange for this offence, I am sure that many European countries - i.e. France would most certainly refuse. It's really just a question of whether Assange can get there.
Ironically, Sweden would likely refuse to extradite Assange to the US for espionage.