Hi Melissa,
I've used plenty of different slings and carriers to review them for the site. A good place to start for opinions is the product review section for carriers.
You can't breastfeed without taking your baby out of the wilkinet, no. One of the things that is really nice about a sling, as opposed to a carrier, is that you can adjust the position of your baby without taking him/her out, and in most of them you can use a breastfeeding position (also nice and discreet).
The wilkinet is pretty adjustable in terms of the different carrying positions and it does offer more of a sense of security than most simple slings. What you really need to decide is where you fall on the security vs flexibility debate. In carriers like the BabyBjorn your baby is securely strapped down and won't be going anywhere, but in many slings the secuity depends on how you wear and adjust the sling and there will be times when you'll probably want to secure your baby with a hand when bending down etc.
If you want to baby wear a lot of the time, as opposed to carry your baby for short-ish stretches then my personal recommendation would be to go for a sling. Do remember though that you'll need to either swap your baby from shoulder to shoulder, or opt for a sling that uses both shoulders to bear the weight (usually a bit more fiddly). Have a look at the product reviews and, if you can, try and borrow a couple from friends to try out, as they are quite a personal product and what one person finds easy and comfortable to use, another person may find a fiddly nightmare.
this might not be much help, but I personally found that I reached for a different sling or carrier depending on the circumstances and on my baby's age - mine loved the carrier styles as a little one, but by about 8 months far preferred the flexibilty that a sling style offered.
