I know these forums are read by people thinking about taking the c25k plan and also think I know a little about how they feel as I was thinking about it myself just a few months back. Hopefully some of my experiences will help you think about doing the plan.
I hated running at school. In the cross country I used to walk most of it and regularly come in nearly last. To balance that - I don't think I was very very unfit - I just hated running because i can't do it. Running was not for me, my body's mechanics don't support it, or so I thought. I used to try at the sprints (100m) but I was hopeless coming in last even though I was trying. Further support that my running mechanics aren't there. After the first few months of that I coasted the rest of my PE years at school avoiding giving more than I had to to try to avoid being the PE teachers target for humiliation.
Since leaving school I started work and set about getting fatter over the next 20 years. I ended up with a Body Mass Index of 39. In the Obese category.According to wikipedia a BMI of 35+ is probably in the morbid obese category. I used to take pride in my ability to eat drink and not exercise.
Not sure what happened but I decided to change that - when I figure out what gave me that iightbulb moment to lose the weight I will share it.
I did not run when I was very overweight - I dieted, walked and used an Xbox/Fitness video to try and build some fitness.
I started the C25k when I had a BMI of 30. At the bottom end of the obese category. I found the start to running just like it was at school, the first few seconds were ok but soon into the short runs I was out of breath and hating it just as much as the cross country at school.
However, because of my need to lose weight and the amount of calories that a run seems to burn (all the calculators I checked show that running is the best burner of calories minute for minute) I continued with it. Plus, during the program, whilst I felt it was hard I never found it impossible - I just had to keep forcing myself in the last part of each exertion phase. Sometimes I really wanted to pull up and stop but I managed to will myself through it - mostly by slowing down to make it achievable.
Going through the plan the times extended and it became less of a nuisance and more of a ego boost at each milestone. Week 5 is life changing
So, after completing the plan I find that actually I can run - I just needed to get all of my ducks in a row - cardio fitness, leg fitness, back fitness, bone fitness (all of these things had been noticeably improved for me over the 9 weeks) - I might have been fitter at age 12 but I was not trained to bring all the things together. I
After 3 months I am now running further than I have ever done in my life - I've managed 10km in a single run and I can do 8km without really feeling too tired (you have to be able to feel it or else its not exercise but it certainly doensn't "hurt"). I'm not as fast as I want to be but I'm working on that. I can't imagine at school ever thinking it was worth investing leisure time in trying to run faster!
I have been cycling and walking more in addition to the plan. I don't know if that is because of the plan or if the plan made it possible - I suppose one has to look for a more active lifestyle. As your fitness improves these things become less of a challenge that exerts you and more something you will choose to do for fun. I certainly enjoy cycling to the shops more than going in the car - shame I haven't figured out how to get a trolley of essentials back with me on the bike. I spent half my lifetime trying to avoid unnecessary exertion - now I might go to the shops twice a day on my bike if i need to (and time allows of course).
If you are thinking about the plan the definitely get yourself into the right mental state and start it off. If you apply yourself to it then my experience has been that it really is possible. Even for someone who wasted 50% of their life being too fat to enjoy many of the things that having a basic level of fitness makes possible. The things that fitness brings are worth having - that might be running up hill with the kids until they are giggling with exhaustion or it might be just walking way from the crowd and getting somewhere where the cars aren't - whatever works for you. Go on - Do it!