I just wanted to pop in and say I love trail running!!! It's pretty much all the running I do aside from treadmill runs. Hills, I have a love/hate relationship with them. Going up I'm usually muttering "I hate hills... I hate hills" but going down I'm all "OMG I LOVE HILLS!!" You'll find your stride on them with experience. Sometimes I walk them, sometimes run, sometimes a combo. It all depends on my heart rate/breathing rate.