Okay, I'm really happy with how the inventory pages work, except for the fact that it makes buying requests more difficult. It used to be I could add the item bought and take away posts right at the same place in the Admin controls, but now I have to find the buyers inventory page and then edit the post. It doesn't sound all that different, but it does make buying requests take longer to fulfill.
To fix this inconvenience, I will be still placing items in the signature and it will be up to the buyer to place them in their own inventory page. Its just too much of a hassle having to go and edit someones inventory page instead of doing it all in one place. You can make a place in your signature that could read something like: Just Bought Items or something like that.
Anyways, I still plan on keeping the inventory pages for good, unless an even bigger problem with the system is found.