Nope - I bloody hate running.
Tried it one winter when I was at uni in an effort to retain some fitness as I wasn't keen on cycling due to the wind chill / chance of coming off / hardness on the kit. Despite having a "reasonable" level of cycling fitness, I couldn't even get around the block without stopping
Add to that it's high impact and I have dodgy joints (especially knees and have a history of being overweight), plus I find cycling intrinsically interesting and enjoyable (probably due to the range and associated practicality / variety of scenery) while running is just boring pain.
As per Mo's post though they're apparently good complimentary exercises so probably not a bad combination if you're willing and able. I do walk a fair bit in an effort to add a bit of variety.
As for fitness, obviously you're going to get better at what you do most. Cycling has helped me lose weight recently and my asthma's got a lot better too (I've gone from using an inhailer typically at least once per day to rarely ever) although it's possible that this is due to diet / a combination of the two.