Michael, I bought a used 4990 about a year ago and it too came without the original disk. I just d/l'd the drivers from Epson's site and that's all I needed to get the scanner up and running.
I actually like Epson Scan -- in fact, I like it better than Vuescan for one basic reason. When having a batch of images scanned in Epson Scan, I can have individual adjustments done to each photo, whereas as far as I've been able to determine, when doing a batch scan in Vuescan, it is not possible to individualize settings for each image. This is kind of a big deal to me, and enough where I'll just continue to use Epson Scan.
Regarding Silverfast, I've tried it as well, and I consider its user interface to be horrid. But that's a matter of personal taste. Still, once again, enough for me to just stick with good ol' Epson Scan.
Incidentally, I recall running into a similar problem as you when I first got my scanner. I was interested in the original disk because of the other stuff that should have been on it. In my case, I have an Epson 3170 scanner that, on its disk, it came with a cool little image copy function that turned my scanner and laser printer into a copy machine. I liked that, and now that I've idled the 3170, I kind of miss not having that with my 4990.
Oh well.