MISTERSQUID  I'm going to chime in on this one, too. I have the 6.6.1rb SilverFast software for the Epson Expression 10000. The cost of admission for this piece of software was over $300 and it was very buggy in Leopard 10.5.4 through 10.5.8. It stopped working over Firewire in Snow Leopard though, as another poster has commented, Apple's bundled Image Capture can see my scanner plain as day.

My advice is to stay away from SilverFast. Their foundation is aged and creaking and the only hope is that another company will see the gap and step in.  
(Version 6.6.1r2)

GUYCARMELI  I have been a SF user since 2005. I am a professional designer and photographer and used to use SF for my work on a daily basis.

When I purchased a new Mac Pro workstation last year I had to upgrade SF to version 6.6 in order for it to work with Leopard and Intel. Since then it has not worked. Every time I launch it, whether through the PS plugin or standalone, it gives me a "scanner not found" error, and either quits or I have to force quit it together with PS losing my work. Apple's Image Capture and Epson's Epson Scan find the scanner immediately. Ironically, using Windows XP via Boot Camp with the same version of SF works fine as well.

I am a veteran Mac user with good technical background. I keep my workstation up to date, and check it for problems regularly. I can see clearly that this version of SF is problematic, but support only replies with general solutions like reseting, re-installing, checking permissions, etc. I have been very specific in my description of the problem numerous times but I do not get professional and specific responses. I use many other products, and I have worked myself in software companies for many years; I can see clearly when I am dealing with a low quality product. Even when it did work in prior versions, the software seemed outdated and buggy. While the scan technology produced great results, the usability was awful. The interface is amateurish and belongs to the early 90's.

I have tried to post my problem in their forum twice but the post did not appear.

I cannot find anywhere on their site a customer service address, so I sent my request to sales, after giving up on the support team, but I did not get a response from them as well.

I currently do not want any explanations or support assistance - just my money back. I am infuriated and disappointed from this attitude, and surprised by the lack of professionalism. I've never experienced such apathy and disrespect from a "respected" company.  
(Version 6.6.1r1a )

RPPHOTO  Well, I rarely review something that's just bad, but I spent $179 to upgrade to the newest Silverfast (although my estimate before checkout was more like $119; I had put various serial numbers in to see which version would give me the best price, and apparently the checkout process "cached" the one with the highest price. I didn't notice until it was too late since I never viewed the receipt. Actually, I'm using the more advanced version than the one listed here. Anyway, after a few days of experimenting I was finally able to get the stand-alone to see the scanner. VueScan Pro and the Epson software see the scanner without a flaw and without exception, and scan easily. The Silverfast Photoshop plug-in in CS4 still does not work; Photoshop freezes completely and I'm forced to force-quit everything. The stand-alone software in the newest Leopard is a living nightmare. It sees the scaner intermittently, even after following Silverfast's trouble shooting tips. I've tried FireWire and USB with direct computer connections. I'm using the Epson 700. If I'm extremely lucky I can get two or three scans out before everything goes haywire, windows freeze, options vanish, sometimes it won't even launch. Trying to use this software is a real joke, it's costing me thousands of dollars in lost time, not to mention extreme frustration. The implied features of this software are fantastic; it's too bad the SilverFast software engineers are too inept to make them workable. This is a company of thieves and liars.  
(Version 6.6.1r1a )

MICKSMAC  This is horrible beyond description, but I will try. Bear in mind that I only tried the demo version (although supposedly, all features are enabled). I tried it with an Epson 2400 Perfection Photo scanner.

First - it crashes constantly under Leopard (10.5.5 anyway). It is a carbon application, and is launched from a "launcher" application, so your dock ends up filled with 3 or so icons. Some windows spontaneously lose their contents intermittently - buttons and checkboxes disappear.

Second - there seems to be no way, when scanning slides and negatives, to auto-select the multiple frames of the film strip or slide holder. This means you have to manually mask each photo individually and scan it! And then, the zoom-in button doesn't work,. so you have to mask based on a tiny, frame-sized image.

Third - it doesn't default to sensible scan resolutions. Who the hell would want to scan negatives at 150 dpi?? You have to select "other" then use a slider to get maximum scanner resolution. And even then thete is no guidance as to whether you are getting true optical versus interpolated resolution.

Fourth - some of the buttons just don't work (eg. histograms). Maybe these are disabled in demo mode, but this is not documented.

Fifth - no uninstall. I had to use "Pacifist" to pull apart the .PKG files to find where it put all its files, in order to manually remove it from my system.

I'd value the developer's response to the above, so I'm not going to rate it, to be fair. I suggest that anyone evaluate with your own scanner very very carefully. Persoanlly I cannot believe they can ask so much money for this producy when it simply doesn't work at all with my Epson scanner.  
(Version 6.6r2)