Thoughts
I have several ring slings, a mei tai, a Beco Butterly and we've used plain cotton cloth for a wrap.
I like the slings because once you're proficient, there is no faster carrier for getting baby in an out and they're very flexible. For our girls, the sling worked well from birth right up to age two, but DS wasn't as content in the sling after about 8 months.
My mei tai is homemade too. I like it, but the learning curve has limited how much it gets used. I never reached the point where I could get a child on my back without help. What I really like though is that if you're wearing baby for a long time you can change the way the straps are tied to shift the weight and stress around.
I got my Butterfly half price and tax free at a warehouse sale when the Butterfly II came out, but after having used it for nearly four months I think it's well worth the $140 full price. I haven't used it with a newborn, but it's really easy to put on your back alone, you can change wearers without taking the baby out, and it's very comfortable. I do find the waist belt more comfortable than my mei tai after for long periods. I use the Beco a lot, and am sure that I'll continue to use it a lot as DS gets bigger. i might use it less if I was better with the mei tai, but I haven't used my mei tai at all since I got the Beco.
If you have no particular issues with the carriers you have for the baby stage, I would skip the wrap. A new mei tai or a Beco will be useful a lot longer.. Slings are okay with older babies and toddlers, but I think other carriers are better. And since your mei tai is nearly worn out, it sounds like you could use something that would be especially good for a child over twenty pounds as well as with a newborn.
If you're really good with a mei tai, and have no issues with it, a Beco might not be worth the money for you. If you can get the Beco for less than $90 making up the difference, that's what I've seen them going for used... so if you decided to try the Beco and didn't like it and you could sell it and get your cash back to buy something else.