I already own the N656U which is the smaller sister of the N1220U.
When buying a scanner, one of the choices affecting scanning quality is whether or not the scanner uses CIS (contact image sensor) or CCD (charge-coupled device) sensors. Each method has merits. The most expensive photo and film negative scanners use CCD. The thinnest, smallest footprint scanners use CIS.
From Canon's website at
http://www.ccsi.canon.com/scanners/csn1220u/index.html,
the N1220U is a CIS scanner which is one reason why it can be cheaper and smaller in size. Note that CIS scanners generally have less dynamic range than CCD scanners. I have already noted that its dynamic range is less than that of one of my own CCD flatbeds (but I knew that before I bought it). When you buy a N1220U, you are making compromises to gain critical key advantages of THINNESS, LIGHTWEIGHT, and FOOTPRINT. If you use a laptop and travel with a scanner in your laptop briefcase (as I do), a CIS scanner is usually your only choice as long as the CIS scanner is "good enough" and this scanner is certainly "good enough".
ZDNET description of how CIS and CCD work
PCWORLD's comments about CIS versus CCD technology
UMAX statement about usage of CCD versus CIS
There are other informative pages, but I highly recommend that you look at the UMAX link above to see scan examples comparing CIS and CCD. They somewhat approximate my own observations between my own CCD and CIS scanners, although in my case, the differences are a little smaller than that demonstrated at the Umax site. Improvements in CIS technology have narrowed the difference since Umax published that webpage.