It's so important to not get carried away when you are using presentation software. It's nice that even free presentation software has all kinds of bells and whistles and I understand the temptation to try and make your presentation as interesting as possible.
But putting all kinds of special effects into it just makes it confusing and makes it look unprofessional as well. If you are going to use a special changeover for the slides, stick to just one of them, and make it simple, like a fade out.
I have to sit through some really ostentatious presentations in my work and it gets really annoying after a while, because it just distracts from whatever message the person is trying to put across.