Canon USB powered devices
I had (and still have) very good experiences with canon scanners. I am using a canon N1240U (2400x1200dpi, bus powered USB device). The problem is driver support. The actual drivers (CANOSCAN v7.0) are for photoshop use only, which is kind of stupid. But it works great with VUESCAN, a standalone scanning software, a must have (check versiontracker). It literally supports almost all scanners, inlcuding SCSI ones, within OSX.
Another solution would be, not to use the new OSX drivers from canon , but the CANOSCAN OSX BETA drivers (v.6.2) which came out one year ago and was backdrafted by canon a couple of days later. Because it gives you twain scanning support within GRAPHIC CONVERTER e.g. (another must have) or any other software which supports it. And I don´t know why they took it away, because it runs smooth and stable for quite some time now with me.
G.