Hi L.! First, congrats! It looks like you've already received tons of responses already, but I thought I'd give you one more. There weren't that many messages from folks who actually use gDiapers and the inserts on a consistent basis, so I thought I'd give you my two cents too. My son is now 16 months old and we have been using gDiapers since he was about a month old and haven't had any problems - we actually have more leaks with disposable diapers (maybe I'm just out of practice!?). He was not breastfed so we didn't have to deal with the explosive breastfeeding poop, but he has had some "interesting" poop (you too will become a poop expert).
The gDiapers are used in three parts - the outside cover, an inner liner, and the disposable part. For the disposable part - we only flush the poopy diapers and have never had a problem (you just tear down the sides, everything falls into the toilet, if you need to you, have a "swish" stick to break anything up, then flush), the diapers with just pee can be composted or thrown into your green waste garbage bin (with the looming drought, we're trying to conserve water where we can).
If poop gets on the inner liner, I just give it a quick rinse and toss it in the laundry, rarely does poop ever get on the outside cover, sometimes he does leak and pee gets on the outside cover but since its an absorbent cotton it doesn't tend to soak his clothes or bedding the way a disposable leak does.
The other benefit over plastic disposables (aside from not living in the dump for years and years and years), is that they are much more breathable - the only times our son gets diaper rash is when he's in a disposable. For those couple times, I've used pre-folds in the gDiaper to really let him air out and dry up.
Anyway, I've been really happy with gDiapers using the inserts (grandma who babysits 4 days a week also uses them without problem). I haven't found the cost that outrageous (for the benefits) - I buy them online from diapers.com. There is also a really active gDiaper's Yahoo Group that you can join (http://groups.yahoo.com/group/gDiapers/).
Congrats again and good luck!