Hey Andrea, who are you hosting with? That would be the first thing I’d take a look at. I know from experience that GoDaddy is usually super slow. So if you’ve got them you might want to consider switching web hosts. Another thing you should take a look at is how much memory is allocated for your site. You can check with your web host to find out and/or just try increasing it yourself: http://www.dailyblogging.org/wordpress/increase-wordpress-memory-limit/
Other things to take a look at are:
1. Other plugins.
2. Your theme and how clean/optimized the code is.
3. Consider using a caching plugin to help boost performance overall – I almost exclusively use this one: http://wordpress.org/extend/plugins/w3-total-cache/
4. This article goes over a few other things you can look at: http://codex.wordpress.org/WordPress_Optimization
I doubt it’s anything with the plugin itself because it’s really gone through the wringer to make sure it’s optimized for speed and scalability.
I hope this helps and I hope you get the speed issues worked out.