Ralph,
I can try to answer your questions from my perspective of course I'm not "Trail and Era" but I do work with them.
For BPL customers there currently may not be any big advantage to buy from Trail and Era instead of directly from me or others. They do offer free shipping but you still need to wait to have the products built. However, most people aren't as aware of all the small shops like mine and others as the BPL crowd. Partners like Trail and Era help connect our brands to customers who don't know us. The benefit to those customers is that the Trail and Era team uses the gear they carry and can give good hands on advice to customers looking for help with unfamiliar and new (to them) concepts.
There is also the benefit of having all these gear makers available at one place. Again this may not be as big a benefit to the BPL crowd who know every gear maker withing minutes of their inception however it helps those looking for lighter than REI gear but not spending hours a night scouring the reaches of the web to discover it. Bringing a lot of great gear to one place helps for comparisons too.
I know their plan is to move towards a physical store in the future so more products will be stocked and ready to ship down the line which would allow ordering multiple products form multiple manufactures on one order, from one place and have it all arrive in one gloriously huge box at one time.
I like these guys a lot and I think if you talk to them for any reason you'll find it hard not to smile as you listen to their heavy NYC accents, fun guys:)
-Tim