If you get the driver to install and recognize the Epson as a scanner, then Vista's built-in scanner software will allow you to use it natively as a scanner without the need of extra scanning apps. Some HP all-in-one's, for example, work well this way because their scanning capabilities are recognized, while other HPs don't scan at all because they only get recognized as printers/fax machines, even using HP scanning software. From what I've tested so far, if the Epson is not recognized as a scanner by Vista, then the other generic scanning software should not work.
I did get the scanner to work last night. I managed to find the setup wizard for the scanner and after a period of Vista insisting that I was installing a Xerox scanner, I finally beat it into submission and it showed me the list of scanners it had software for, and the Epson 1660 was on the list.