I've lost about 2 and a half stone since June through a combination of lower calorie diet using MyFitnessPal (massively reducing intake of sugar, bread and potatoes has been key for me I think), making sure that what I have been eating has been fresh and healthy, and doing exercise about 4 times a week (mainly swimming and the Insanity DVD - some running as well although not as much in the winter).
I've piled nearly half a stone back on through eating and drinking too much in December (I didn't mean to 'write off' the whole month, but I effectively did.....next year will try harder not to do that) but I'm not worrying about it, I feel confident that getting back into my routine will get me back down to where I want to be fairly quickly.
Building in 'cheat' days every couple of weeks, where I eat and drink whatever I want (ice cream, chippy, chocolate, lager etc) has been essential to keeping me on the path as I know I'm never more than a few days away from 'treating myself' - that has been a major factor for me psychologically, I think.
I think it helped that my boyfriend and I did it together - it's helped with motivation and planning meals, making time to exercise etc. I think I would have lasted a couple of months on my own but possibly not sustained it as well. We don't have any children though so we don't have that added pressure on our time and priorities - again I'm not sure how I would have managed it around parenting responsibilities.
I would never previously have thought of myself as a calorie counter (seemed diabolically tedious to me) but the app on my phone made it (a) quite easy and (b) made me realise actually how much I was eating (probably taking in about 3500 calories a day easily - I was in denial about that). I can now comfortably live within the range of 1200-2000 calories a day now (I try and mix it up a bit) and almost never go to bed hungry.
Best things - since about September I've had a steady stream of people telling me that I look great, they're really impressed, etc. I've absolutely loved that and it has been a real ego boost. I've graduated from feeling repulsed by photos of myself to not minding them too much (I am not really what you would call photogenic but I fell that I don't look too bad, which is good enough for me).
I feel loads fitter and it has been a real thrill to realise that I could manage parts of the Insanity routine that I simply couldn't do a few weeks previously. I fit into clothes I last fitted into when I was 25, and I feel that I look better in them.
It's helped me start thinking more actively about doing other things to make my health better, like prioritising getting more sleep and keeping my alcohol intake down, and I feel more positive about the future (I'm 32 and had just started thinking about the likely consequences of my health choices on my health when I'm older - my Mum died at 58 from COPD and that doesn't seem massively far away any more). I do want to have a family of my own and taking control of my health feels like a proactive step towards that.
I think this is probably the longest I have ever sustained a (what I consider to be) a healthy lifestyle (6 months). I can't say it will last indefinitely - I am taking it it as a 1-day-at-a-time thing but it has really helped to see a difference. I would say that it took me about 3 weeks to start feeling a bit different and 7 weeks to see any discernible difference in my appearance - but then I could REALLY see it. So the lesson I have taken from that is to stick with it through the first few weeks and don't get disheartened - the change is imminent.
Good luck with it - it's DEFINITELY doable and definitely worth it.