An app like this may seem like a novelty. It did to me up until last month. I had tried at least three "scan to pdf" type apps and dismissed them all immediately due to poor functionality and results. The pdfs created weren't clear enough to be printed and look normal. This included Droid Scan.
Then I tried Document Scanner. It worked great, and in less than a minute I had a readable, printable two page pdf file ready to share. First problem was huge file size.
Something I'm noticing while comparing CamScanner with Document Scanner is that Document Scanner produces MUCH BIGGER files than CamScanner does for the same document and lighting conditions.
I found that converting to black and white reduced the file size to something closer to normal, producing 200-300kb pdfs containing two [originally] 8mp photos of A4 paper documents. There is also the option to use the stock camera app, and it will import the pic. This seems to take a lot longer than the other options, and the resulting pictures are not as clear as they were when untouched or converted to grayscale.
I couldn't stand the crop tool, however, which is a 100% deal-breaker. It's so small that selecting the desired location is a frustrating waste of time. So now I've been using CamScanner.
I had two work orders today, and had to either fax them in or scan and email them in (as pdfs to be printed) by the end of the day. I normally drive somewhere to fax them in, which is a waste of time IMO, and while I have a scanner at home, I don't want to do paperwork at home. Ever. Today I emailed each one in using CamScanner while still on-site. Saved me an extra trip, clients thought it was awesome when you explain the process as you're doing it. That's worth its weight in gold. Fortunately, since this app weighs nothing, I'm only out a few bucks. I'm buying this one. This ability to generate a multi-page pdf from phone pics is amazing with the proper software. I estimate it's saving me 8-10 hours a month, if not more. Phones sure have come a long way in just a year.
I think apps with this functionality will be far more effective another year from now, and likely more streamlined. But CamScanner is already at the point where it can replace a fax or scanner for A4-sized B&W docs and not be noticed.