I've recently started scanning a collection of probably 8,000 kodachrome slides. I don't think I'll live long enough to see it completed! I have the Epson 4990 (same as Rusty has) and it does an terrific job on slides. The Digital ICE feature that removes scratches and dust is amazing but applying it does add a lot of time to each scan. It scans 8 slides at once. If you are interested in seeing some befores & afters using Digital ICE, send me a PM and I'll try to get something posted for you.
I have an older HP scanner-3900 series, I believe. It was $99 when I bought it at Best Buy 3 years ago. It works great (though it's the only one I've ever used, so what do I know?). The one thing that I am going to look for when I replace it will be the ability to clean under the glass. I live in an old dusty house and I have dust under the glass and I can't clean it, so I will be needing a new scanner when I get tired of cloning out all that dust. That might be one thing you want to look into.
Deb