I've noticed this issue from the last few builds, and it appears every-time I update SD the UI will become extremely slow when searching, and browsing the library.
After looking at this in greater detail I'm guessing that because each update uninstalls the current SD version, and does a fresh install, something either with the database, or some file directory needs to rebuild. I'm assuming this because my disk usage goes to 100%, and if I leave SD open for around 20 minutes and wait until the usage drops off, I just have to reload SD and everything populates and is smooth like before.
I've also tried "restarting", and various other tricks with the registry but nothing seems to work unless I just let it do it's thing.
Is this normal for everyone, or is there a reason everything needs to rebuild for me? I just have to make it a habit to do my updates end day, and not during working hours.