I've used Barcode Scanner since I first got my Droid.
Every app will have mixed reviews if you look into the reviews. Barcode Scanner has 4.5 stars from 174558 ratings (according to Appbrain). I'd consider that to be very good. Yes, there are poor reviews but if you're going to dig down into the details then you need to learn to read between the lines. There are a lot of poor reviews in the Market that are clearly from clueless people.