On Linux and Windows, LibreOffice is quite broken on high-res screens. The text look great, but every bitmap is too small to easily recognize or click on, the spelling underlines are hard to see and too close to the text, etc. The Mac doesn't have as much of a problem because of this: https://developer.apple.com/library/mac/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/CapturingScreenContents/CapturingScreenContents.html. I've created a wiki page to track progress: https://wiki.documentfoundation.org/Development/HiDpi, but it is helpful to have a bug report also.
A set of patches have gone into 4.2.3 rc1 that improve things: http://cgit.freedesktop.org/libreoffice/core/commit/?h=libreoffice-4-2&id=52cb1085edc66995393d5be5a55cb45b73a95292 http://cgit.freedesktop.org/libreoffice/core/commit/?h=libreoffice-4-2&id=8f805c57aadab54de421b0f961d0cbda9fa6d386 http://cgit.freedesktop.org/libreoffice/core/commit/?h=libreoffice-4-2&id=ab2739b37d8c331aa5ed26346c7e29199a369571 http://cgit.freedesktop.org/libreoffice/core/commit/?h=libreoffice-4-2&id=dfffb3244a4fd8cd58fa7786cbec626604dc61e1 http://cgit.freedesktop.org/libreoffice/core/commit/?h=libreoffice-4-2&id=a644b400d611bfa086e0cdb6b0a41228809ffd3d http://cgit.freedesktop.org/libreoffice/core/commit/?h=libreoffice-4-2&id=ce5c798868e33c094971d8b8c2c9f40afc8f21c3
Here's another fix that has gone in to 4.2.3.3: http://cgit.freedesktop.org/libreoffice/core/commit/?h=libreoffice-4-2-3&id=b740953537b324e157b22ce3bd46611b01f78e47
Another fix is queued up for 4.2.4 to fix fdo#77059 http://cgit.freedesktop.org/libreoffice/core/commit/?h=libreoffice-4-2&id=bcba071c0d583a0b3a62d6d718829b906ecc37f2
There is more work to be done, such as better bitmaps, but with all the patches already checked in: http://cgit.freedesktop.org/libreoffice/core/log/?qt=grep&q=hidpi this bug can be resolved. LibreOffice 4.4 looks great, and 4.5 will be even better. There isn't too much pixelation with Tango or Sifr, but it could be better...