Got my M40 grey/red bik's on Tuesday from citysports. I may have ordered the wrong size, so the following comparison might not be as accurate as I'd like. In brief, I sized down due my first KSOs were M42 and are now fairly loose (I attribute this to all the strengthening my feet have gone through since last April when I got my first pair). Next I ordered the Treks in October last year in M41. At this time, foot measurments said I should wear a M40, but I decided not to drop 2 sizes and went with the M41. Both pair of my Treks are M41 and fit ok, though a tiny bit loose (this I am attributing to the leather stretching a small amount). So now I decide to try the M40 that the foot measurements said to use. I heard the Bik's should fit glove-like so that's what I went with.
Now that is out of the way, I must say the Biks are a bit tight. Maybe TOO tight. I tried a quick trail run (fairly smooth with minmal rocks and roots, mostly hardpack dirt) on a nearby loop. I really didn't like how they felt. My toes seemed to be getting quite squashed up front. I made one loop then switched back to my Treks. Oh what a relief! My feet were quite happy with this.
After getting home, I threw ALL my VFFs in the wash (it was time, as they were getting more funky than usual.) I decided to go ahead and wash the Bik's due to someone that had posted this helped to loosen them up. I put them on soon as the wash was done and really didn't notice much difference. As far as fitment goes, I've only had them 3 days, so hopefully a little breaking in or just getting used to them will improve things.
Now on to feel. To me, the Bik's definitely have a 'firmer' feel to my Treks, though this is likely to the age difference (treks are 6+ months old, Bik's are brand new). During the initial trail run (yeah, I know, road vs trail shoe, etc), the feel of the ground was about equal, on the hardpack dirt. Going over the rocky sections, not so much. The Bik's were much less sure-footed there. I could really feel the rocks wanting to 'bite' into the foamy arch area and a couple times I thought I might have poked into it, though after checking, nothing even marked it. I did notice on one particularly large slab of rock on a short uphill section that the Biks stuck REALLY well. The low profile did let in a bit more grit than the Treks.
I do not recommend Bikilas for any kind of trail running. They MIGHT be ok for well-groomed hike and bike type trails (wide, flat with crushed gravel) but not at all for anything more robust.
For general walking around/casual wear, the jury is still out. IF I had purchased the larger M41s, I'd probably be able to better compare with my treks. I do like the softer lining in the Bik's and they seem to be a bit cooler than the Treks (temps are about 90 yesterday and today). They also feel slightly less tight today than yesterday. The lower profile is also nice, as that's less skin being covered, and thus cooler.
I like the Biks, so far, but am not in awe of them (again, possibly my fault for getting the smaller size.) I think they compare pretty well to the feel of the treks. Both the Treks and Bik's have way less feel then my KSOs, so the actual difference between the Treks and Bik's might change a bit with use.