I'll throw my 2 cents in here too, definitely not a pro but someone looking at biking as a way of getting back in shape, I hadn't ridden a bike in over 25 years. I'm also on the heavy sided at 6' 250lbs. At the time I got my bike I had just started riding again and had tried a GT 29'er that a friend lent me from Sportcheck, a Specialized Crosstrail, a Brodie hybrid (non-forked) and some other random Norco 26" MTB, I eventually settled on the Trek 8.4 DS just because of specs for the price. I sampled both V-Brakes as well as disc brakes and found that I really liked the responsiveness of hydraulic disc brakes over V-brakes and mechanical discs. Also after riding around a local trail that had a combination of pea gravel/singletrack/pavement I found a lockout capable fork to be what I wanted. At the time I did not have a bike rack so transporting a bike around meant taking the front wheel off before shoving into my hatchback (I quickly ruled out the V-Brake bikes because of that). Ultimately, due to lack of experience all the bikes felt the same and I made my decision soley on price vs components. In Vancouver last August I was able to get about $20 off MSRP during the end of season sale whereas every other shop was quoting full MSRP. I paid $899 rather than $919, (I ordered via my LBS's website as I had about $150 of Paypal credit kicking around)

I was quite surprised on pickup (My colour/size was not available at the LBS and they had to move inventory from one store to another) that the Tektro brakes and hubs had been replaced by Shimano parts from the 8.5 DS, I can't say if this was due to Trek running out of parts late in the year and just using the next best thing? As you mentioned you are commuting, I got the Bontrager NCS fenders and a Topeak MTX rack installed, and I changed out the hard as heck saddle and now run a slightly thinner 700x32 more road orientated tire. Once I started riding a bit more I found I was having shoulder issues and had the stem changed out to a longer one, and the ergo grips on the 8.4 to be rather crappy and had a little bit of vibration/movement due to how they were designed, those came out and i got some new grips with bar ends just to change up the hand position.