It has been reported that the UI on Windows version of Siilihai is slow. Also the installer size is almost 100 megs which is huge.
Current versions of Siilihai are built with debugging on. This increases the file size and makes larger binaries. As Windows lacks proper package management the required Qt libraries must be included with the installer. Qt's libs with debugging symbols are huge and explain the size and slowness of Windows build.
Releases without debugging on will be made after 1.0 is reached. It is probably be pretty soon, as the current version seems to work really well. I estimate that the non-debugging installer size will be around 20-30 megs.