T Allen asks a valid question, and I'll answer them from my perspective--amybe this'll shed some light on what you need.
My hobby-turned-everywakinghour-project:
Digitize my family's analog history: photos, 1/4" reel2reel, 8mm film (might have a service do that), and
slides. My father was quite the shutter bug in the 50s, 60s, and early 70s with slide film. I have 20 carousels with 140 slides per (±2800 in total).
T Allen's Q:
How are the images are going to be used once they're digitized?
A: My goal is to use iDVD to have on TV slide shows; however, I can use them to in iMovie>>iDVD, etc. Since print enlargements (thus 2700+ dpi resolution) are not a priority, I chose to purchase a flatbed scanner with a lightlid: Epson Perfection 1650 Photo.
This gives me a high enough resolution (±1900x1200) that I
can print a decent 5x7 @ 240+ dpi on a photo printer--or through Ofoto, but mostly because at that rez, my 12 year old nephews' future kids will be able to watch them in HD (1920x1080) :-). I'll knock down the res to NTSC (or therabouts) for my immediate plans.
Obviously the Epson is not a pro scanner, but it serves my needs and budget for cataloging and what not. It will scan 4 35mm slides at a time and take about 8-10 minutes to do so @ 1600 dpi. The real time consuming part is naming the TIFFS and cataloging the slides.
Not much X support--yet (I'm scanning in OS 9). If you go with a dedicated film/slide scanner, be prepared to spend over $500 (though
SmartDisk--announced a 2700 dpi scanner for $250). Another quality flatbed is the Perfection 2450 PHOTO Scanner (2400 dpi, FireWire) for $399--check out Amazon for customer reviews.
Scan at the highest res avaliable. While it might be slow, it's faster than rescanning.
Have fun.