After slowly getting frustrated at my Air's problems with safari and other app crashes I decided to call Apple about the issue. Having sent them the diagnostic logs the Apple rep said it would be best to do a clean instal via iTunes and not a reset on the iPad, which I'd done a week or so ago but had made no difference. He suggested that there may have been a problem with the initial iOS image on the device and by reinstalling via iTunes will overwrite any problem. The rep did say once you feel the issue is resolved, restore your apps etc from backup. But to be honest I've just reinstalled everything from scratch. This may not fix it for everyone but I've not had one crash in 10 hours of usage with 5-8 tabs open in Safari. Prior to this refresh I'd be getting a couple an hour at times. I'm glad it's fixed, it was almost a drive to kick up a stink in my local Apple store!