Stephen,
W2D1 - Done !!
Honestly it felt no different then then WK1 to me.
You are right, it is different when you had done it before. You know you did it once and it can be acomplished again. Most importantly I think you touched on regarding your knees. Being a runner before you know what "normal" running pain is and when you need to be concerned. Myself, the last time I ran I had to be really careful with Plantar Fasciitis. Inserts were a given and it kept it under control.
Any thoughts on graduation from C25K? I know the last time within the first couple weeks I registered for a 5K. Running a 5K was my reward to myself for completing the program. I was looking and I do have a 5K one week after I should finish the program. My only issue is in Feb the weather can be pretty cold for running outside. Oh, my motivation running is races. Sure I am slow and middle of the pack and will NEVER win my division but it is a lot of fun and a good way to collect tee shirts.
Mike