Ive just got a RS and I wish I had had it sooner, highly reccommended for BF and cradle carries, es is 14lb and its still very comfy/easy to do it and I can see it being useful right up till she is a toddler. I like the RS better than my Close for BF, its a better position and feels more secure plus you are very hidden. She also looks so so cute in a kangaroo carry! its also great for quickly popping somewhere like paying for petrol, school run in the car etc.
The site Kalia has put a link to is fab and there forum is amazing for education in wearing. I have a zolowear ringsling and its fab, my top tips are make sure you get a strong woven fabric (so that it is supportive right up to toddler) a good amount of material in the shoulder to spread it wide for comfort, measure yourself to make sure you get the right size and try not to get hooked!!!
personally I like RS/MT's/ssc as Im not confdent on my wrapping abilities and dont think my DH would get it at all, but I think it just takes practise if you did want to opt for that style of carrier.
If your not sure then get yourself to a sling meet to try a few out, some of the babywearers on there have many wonderful types of carriers and will more than definatley want to show you how to wear/let you pratice
Carriers do seem costly for a 'bit of material' but you need good quality and well made for saftey, some of the cheap ebay ones worry me that they will be too thin and wear out fast/not be supportive enough. Initial outlay will mean a good carrier you can use right up to LO being a toddler (and any siblings too!!) Honestly I have not used my pushchair more than 5 times since Es was born and that was only because it was too wet to wear/I was ill/hubby insisted, its just so much easier to wear her and if you dont like the carrier they sell on very well