Lee Rigby's family have criticised Apple:
http://www.bbc.co.uk/news/technology-35595840
The article is worth a read if, for nothing else, the short video clip at the top from Chris Foxx which lays out exactly what the FBI is looking for:
1) the ability to circumvent the "wipe iPhone after 10 attempts" feature, which is an optional setting (i.e. not all iPhones do this)
2) the ability to circumvent the delay feature, which means that as you go through the 10 attempts, you have to wait longer between each attempt - e.g. hours rather than a few second (i.e. this is not a quick way to wipe an iPhone)
3) the ability to try multiple PINs electronically, rather than by hand
Taken together, the above three requests would suggest that what they're after is the ability to gain entry to a physical iPhone via a simple brute force attack (trying up to 1 million PINs).
One rather good point made by Lee Rigby's uncle was: "If a court issued a warrant in the UK or United States to search somebody's house, you wouldn't stop them, you would allow them in - why should a smartphone be any different?" If that somebody had a sophisticated security system on their house, and the supplier of that system refused to cooperate with the legal authorities to allow them to gain entry to the house, then that supplier would be doing the equivalent of what Apple is doing ...