yes, I opened both House of Flying Daggers, and Oldboy U.E (which came yesterday and is fabulous).
As long as you keep them in tiptop condition (dont loan them out) then there really should not be a problem.
As far as HOFD is concerned, just buy a replacement 2 disc EDKO dvd, and you can open the one that came with the box.
In the case of Oldboy, the outerbox (pink with ribbon) the seal was already opened, because Starmax posted out inlay cards to retailers to stop the rivets on the tin from damaging the disc cases (as they had loads of complaints earlier on). It's not a problem for this set as the disc cases are not sealed anyway.
I don't intend selling either unless they really shoot up in price, but to answer an above post I do think dvd will keep/increase in value for these Limited Editions for true collectors, as it is not all about the discs. I think Oldboy only had 2700 UE's made, and HOFD had 2000.