When I first started C25k I had a very cheap pair of trainers and then after a month or so went to a well known high street sports shop and was advised to buy a pair of Asic Gel 1170's.
I have been running in these for 7 months and other than one pulled calf muscle have not had any significant problems. However I have over the last 3 month considerably increased the amount of running I have been doing and a few weeks ago I noticed I had some tenderness in my shin and then after another run a sore ankle.
I then decided to have my gait analysis done at Sweatshop. They said the Asics had some slight support which I didn't particularly need but didn't think they would be doing me any major damage. At first I went away with a pair of new Adidas trainer but after two weeks didn't get on with them and returned them for a pair of Mizuno Wave Rider 16's. Since I have had them I have run in them 3 times and they have been very comfortable.
I thought I would rotate my trainers and use my Asics when it was muddy or wet, however I put on my Asics (they were to hand) and did a short treadmill run. I could not believe how uncomfortable they felt, my shin was killing me and my calves were cramping up and I'd only been running for a few minutes. I stopped the treadmill and changed trainers and the difference was shocking, I'm now sure the trainers have had something to do with my sore shin and ankle. I think I probably got away with wearing the wrong type of trainer while I was doing less mileage.