Thank you for the 'welcome' replies'. I've read accounts here from a few others who have been 5:2ing for several months already and I'm happy to share when I can find the time to stick a few thoughts together.
Having had my interest set off by Michael's Horizon (my wife has also followed his Twitter account since then which has thrown up lots of additional interesting bits and pieces), I have done some wider reading on the subject (and there are some excellent resources on this - and other - sites now appearing), what's interesting is that intermittent fasting obviously has a long history. While it has perhaps stayed under the mainstream media radar until now, there are folk out there who have been doing variations on the 5:2 for a lot longer than the six months I've been at it.... so I guess theirs is the real 'long-term' experience?
Still, one quick comment for those just getting started and it's nothing to do with weight loss or long-term health benefits and more to do with maintaining the 5:2 pattern... after six months, 5:2 now feels totally 'normal'. I've pretty much reached my target weight and, some weeks, will do a 6:1 rather than a 5:2. But what surprised me (at first anyway), was that I feel a bit guilty doing a 6:1 and, by the time I've had 6 days of eating normally, I am really ready for a fast day (yep - I kind of look forward to it) - and it's not just mentally - I feel like my body is looking forward to a bit of a breather as well.
I guess what this feels like is that my body as adjusted itself to this new pattern of eating and now sees it as normal. My weight is stable and I feel pretty good on it.... so the message for those just starting might be that, for some (and maybe I'm just one of the lucky ones) a 5:2 pattern can get to the point where it feels totally normal.... and just not a big deal to manage or maintain.
Not sure if that's encouraging or not? Hope so

John