After installation of LibreOffice 3.5.4 I made a comparison of file open time in LibreOffice Writer and Apache OpenOffice 3.4 Writer
These particular RTF files were opened in LO very slow, 6-12 times longer than with AOO.
My friends also tried to open them (in other OSs too) and confirmed the issue, so I think that it is OS-independent.
Feel free to contact me if you need more information or need more testing.
Created attachment 62535 [details]
File 1 in question
Second slow loading file uploaded to http://depositfiles.com/files/xbq4ciuxu
Confirming in 3.5.5. That is probably another outbreak of russophoby from developers.
We already have bug 44736 for RTF import performance problems. Please also try 3.6, it should be faster, even if it's still a bit slower than it was in LO 3.4.
*** This bug has been marked as a duplicate of bug 44736 ***