Pro:
Indexing a drive make the search for a file or folder faster, in some cases, a lot faster.
Con:
When the indexing process is indexing a drive, it can make the system somewhat sluggish.
The index table is saved as a file and can get rather large.
If the content of the drive changes often by having lots of files modified and new files created and deleted on a regular basis, the indexing process need to run more often and will take longer.
Indexing is not an essential feature and it's usefullness can vary greatly from one user to another.
Finaly, if you rarely perform searches for files and folders, you can disable the indexing for all drives.
If you routinely search for files and folders on your computer, you should keep it active.
Electro, October 2012
