I have four big irritations with the behaviour of the installer, which, as far as I know, have all been present since before LibreOffice forked from OpenOffice.  

1.  The Windows installation program for LibreOffice starts by asking where to save unpacked files.  The user has to choose a location, then has to click the 'Unpack' button.  The default location offered is on the user's Desktop.  Once the installation is complete, the directory to which the files were unpacked is left in place.  This directory is used only for the installation, not for running any of the LibreOffice programs.  The need for this directory is therefore temporary.  It does not make sense to:
(a) use the user's desktop for a temporary directory;
(b) ask the user to choose the location of a temporary directory, given that all operating systems provide directories for this purpose;
(c) label the 'Unpack' button as such - such a term may be meaningless to less-computer literate users - something like 'Continue' would be a better choice of word;
(d) leave the temporary directory intact after the installation - it should automatically be deleted.  
The only situation in which it would make sense to ask the user for the location of a temporary directory would be when there is insufficient disc space in the filesystem that holds the operating system-designated default temporary directory.  In such a case the installation program could offer the choice of a directory in a filesystem that it has calculated has sufficient free space.  
I can think of no other application installation program that does not tidy up after itself by deleting a temporary directory and the files it contains, unless we go back perhaps 25 years.  

2.  After unpacking, the next interaction is to ask for the user's name and organisation.  This question is asked even when upgrading from an older version, for which this question will have previously been answered.  Why does the installer not read the configuration of the older version to obtain this information?  

3.  The installation program creates the appropriate Start Menu folder and entries.  It names the folder with the major and minor version numbers, e.g. 'LibreOffice 3.4'.  If the system has been upgraded from a previous major or minor version, the Start Menu folder for that version (e.g. 'LibreOffice 3.3') is not deleted - it should be.  

4.  The entries in LibreOffice's Start Menu folder all begin with the word 'LibreOffice', e.g. 'LibreOffice Base', 'LibreOffice Calc'.  Surely this word is superfluous, since they are entries in a folder named 'LibreOffice ...'?  This is not just a cosmetic issue: it means that the user cannot start Impress, for example, simply by pressing the 'I' key in this menu folder - instead you need multiple presses of the 'L' or down-arrow keys, followed by return.  

I feel these issues add up to making LibreOffice look far less professional than it deserves.