The Ergo was my first non-front pack baby carrier so I will always have a fondness for the Ergo. And my back was quite thankful I bought it.
The Ergo is terrific because there are no dragging straps, it's super fast to put on, very short learning curve (see www.the-ergo-lady.com for more tips and tricks) and husband friendly. The pocket is great for small items. Very, very nice carrier for a mom starting out with baby wearing and it fits most people fairly well.
Despite the wonderful qualities of the Ergo I did end up transitioning to mei tais and wraps because I needed to do a high back carries. Hikes and grocery shopping when I was walking my son was perfectly content however, when I was standing still cooking, he was constantly fussing and leaning side to side trying to see what I was doing. The only other complaint with the Ergo is that, when my son is in a front carry, sitting down causes the wide waist belt to dig into the top of my thighs (not too bad though). I don't have that problem with my mei tais or wraps.
Over all I highly recommend the Ergo and I still use mine on occasion, especially when I need to carry my two kids at the same time.
M'Liss