I got my Babybjorn from a friend in Sweden who had used it for her two children and I can't reccomend it enough! It's so easy to use, doesn't have any complicated knots or loops to work out, is simple to adjust as baby grows and quick to adjust to allow dad to use comfortably too (and also doesn't look too mumsy or 'flower-powery' as my hubby calls it!).
I used mine from when my son was three days old, and it's been everywhere with us! In the early weeks when my babe wasn't sleeping very well I used it to help settle him to sleep (pacing up and down the living room!)- the amazing thing about the Babybjorn is that it's so easy to put your sleeping baby down without waking him. As my son grew we just kept him in the Babybjorn rather than put him in a pram - it made days out so easy not having to worry about finding lifts or ramps, and if we ate out we'd just unclip the front and baby had a padded surface to sleep on. It also allowed for comfortable discreet breastfeeding, which was a great help the first couple of months.
My son loved the view once he was big enough to turn around and face outwards, and we always get admiring comments from passers by! He's now 7months old and still loves his carrier, at 22lb he's only just starting to feel a bit heavy if we're out all day so we've finally had to purchase a buggy, but for quick trips to town we always prefer to leave it at home and take our Babybjorn instead!
For the amount of use you'll get out of it it's definitely a worthwhile investment - and Babybjorns fetch a great price secondhand once your baby's grown.