Well, first, we need to know what your budget is for the scanner, since that will play a large part in our recommendation to you. Secondly, will you ever want to scan-in 35mm slides or negative strips? Lastly, Is speed, cost, or size of any concern? Oh, and are you designing for print or web?
Epson makes some great inkjets and high-end scanners (for Mac and PC), but the low-end to mid-range, IMHO, is dominated by Canon.
Canon's LiDE 20 and LiDE 30 scanners for example are excellent USB 1.1 sub-$150 CDN scanners that are very small, light, and totally Mac compatible. Best of all, they use a high-intensity white LED for scanning and not a bulb; you'll never ever need to replace the bulb. These two LiDE's are just that though - low-end. I have a LiDE 20 and it works great. Got it for $89 CDN at Wal-Mart.
Ultimately, as a graphic designer, you'll want a combination of NATIVE (not interpolated) high-resolution scanning and bit-depth recognition, the ability to scan negatives and 35mm slides, a USB 2.0 and/or FireWire hi-speed connection protocol, etc. However, those will cost you an arm and a leg. And a kidney or two.