Laura - as others here have already pointed out, trail running is definitely slower. I usually estimate a 1 to 2 min/mile drop in pace. So when I have trail runs as part of my workout program I train by time and not by distance. If it's supposed to be a LSD run, I will walk the steeper hills. I also sometimes trade out a interval workout for a med to high intensity trail run. It is very nice for breaking up the monotony.
As for trail shoes, I have a pair. I like them for the better lateral support they give me over my road shoes and the gortex uppers are nice as well. You can trail run in road shoes, just be alert and watch out for long stretches of trail that slope to the side. These will break down road shoes very quickly and will leave your lower leg muscles very tired.
Living life like there's no tomorrow.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS