Pro Fine grained control over the search index
Include or omit types of files, services, apps, folders, index a given folder only to a certain depth, or only index a certain filetype within that folder. The configurability of the index means that I can find the things I care about (eg not random pdf content, song titles, etc) in a under 4 keystrokes 90% of the time.
Pro Abbreviation search which allows you to find items just by typing short acronyms of their name
Fuzzy matching will do a good job of finding items in the index, and gets better as it learns from the user's choice; eg: given I type 'dw', 'Downloads' and 'Downie' might be suggested. If I select 'Downie', then in future it will appear as the first suggestion.
You can also explicitly assign abbreviations to items, without having to 'train' Launchbar as described above.