I own the Sony cover, too, and a Kindle cover from M-Edge that uses the same corner-mounting system as TMC's.
If the Sony readers had keyboards, as the Kindle does, I might worry about the corner pieces getting in the way. But since they don't, I'm not sure why the bracket mounting system of the official cover would be necessary for us.
For me, aesthetics are important (see my thread about the 350's silver color), and stone-oiled leather, which will acquire surface complexities with use without ever losing its color, is a beautiful option. But additionally, the quality of the materials and stitching make it a more durable option than the official cover, which feels rather flimsy to me and has the disadvantage of lacking a closure magnet or other system (shouldn't a case be made to be dropped?). Sony's bracket system, which is handy, ingenious and unproblematic, is also made of plastic. Not everyone wants that in a case.
The question, of course, is how durable the cover need be for an electronic device with a non-removable battery. Let's hope Sony will change our batteries at least once during our devices' life-cycles, and that we won't long to replace our Readers before we must.
Yes, I might fold the cover back, but I'm still aware of the material from which it's made as well as its look and feel. I'm also especially aware of the look and feel of the cover when it's closed and I'm carrying my reader like a book. It's a nice feeling to glance down in the midst of traveling and see something beautiful.
No official cover owner need feel marginalized by other offerings. We all have different tastes and requirements.
I think we can agree that choice should not be discouraged, and that the first cover offering of this kind should have a chance. Unlike Sony, HMC is a tiny operation. It is therefore far more likely to be sensitive to us and address our individual requests than Sony or any other larger company. For that reason alone, Reader owners ought to be happy about this whether they like corner-mounting covers or not.
§§§§§§§§§§§§§§§§§§§§§§§
The last point I'll raise is the one about price:
HMC's covers for the 350 cost less than their Kindle cover and less than the official Sony cover. No light is included, unfortunately, but shipping is free.
People who want cheaper options and a bracket-mounting case that actually closes should consider the cover by Proporta. A user on the Amazon product page claimed Proporta's leather isn't real, but others have said otherwise. I'd love to hear from a Mobile Read member who owns one.
Once I receive the HMC cover and get the chance to use it, I'll tell you exactly what I think.
The point should never be to get people to buy something that we ourselves own, but rather to let them know from experience what they'd be buying.
Your purchase is separate from mine. It would be wrong for me convince you to buy something in order to reassure myself.