I love my ScanSnap, it is great. If you want to go paperless or get your filing cabinet under control, you should definitely invest in one.
With that said, you do need to do the following to make the OCR'd document searchable in Windows 7 64bit.
1. Install the "Adobe PDF iFilter 9 for 64-bit platforms" patch. Without this patch you cannot search for OCR'd PDF's on your PC. Basically, the ScanSnap scans your document, and then the ScanSnap software uses OCR (Optical Character recognition) to turn than scanned paper into a PDF that is searchable. Without this patch, Windows cannot extract the text and index it, making it searchable in Windows. You can download the patch here.
2. Goto the Control Panel > Indexing options > Advanced > click on Rebuild. This will rebuild the index and make your existing documents searchable. This should be done after installing the above patch. You will need to perform this step after clean installing you machine and restoring the data.