Lite version

Single search instance
Post type search only (posts, pages, products, portfolio, events and any other custom post type..)
Vertical layout only
Generic and Category filters only
4 themes, some features customizable
Category and ID based result exclusions

Pro Version

Multiple (unlimited) different search instances
Post types, Taxonomy terms, Attachments, Users, BuddyPress Groups and PeepSo content as results
Vertical, Horizontal, Isotopic and Polaroid layouts
Post type, Generic, Content type, Taxonomy, Custom field and Date filters
100+ Themes, fully customizable
Taxonomy, Tag, User, Date, ID and other result exclusion and inclusion methods
..and many other features, check the full features list.

The Lite and the Pro version are two separate plugins, thus you can switch from Pro to Lite and vice-versa at any time, without loosing your settings.

See the Pro version live demo!