I downloaded OneBag a couple days ago. By the way, I’m linking addon references to wowinterface now. Yea, I’ve complained before about their search results, but I’ve figured that out. They just return every addon that mentions the addon you’re searching for. Makes some intuitive sense, but there doesn’t seem to be any relevance ranking, everything is just listed in alpha order. So the addon I’m looking for might be on the third page of results based solely on it’s spelling. Kind of dumb and I really hope they fix it because I like the site otherwise.
Anyway, I really like OneBag. It had some quirks during setup, but nothing too dramatic. It consolidates inventory management so anytime your bag opens (visiting a merchant, click it open yourself, visit bank, etc.) you see one consolidated interface presenting all the items (and open slots) in all your bags.
OneBag downloads with three supplements: OneRing, OneBank and OneView.
OneRing adds your keyring to your OneBag view. OneBank adds support for your consolidated bank view (including your extra bank slots). OneView is a mini-map button that you can click to open the mega-consolidated view (bank and inventory and keyring all from one window).
The add-on is well integrated and I haven’t found any occasion where OneBag didn’t open or present inventory properly. In fact, if you’re using any kind of unit frame add-on you could get rid of your on-screen bags altogether. I haven’t been that brave yet, but probably sometime in the future I will.
EDIT: With the integration of OneBag into your UI, clicking any of your bags will bring up OneBag. So if you’re not ready to delete all your bags off your screen you can definitely reduce down to just one bag. Clicking it will open OneBag. Also remember that Shift+B is the default UI command to open all bags (just in case something goes wrong).
Here’s a screenshot of the add-on in action. 
Here’s a couple cool things that OneBag does when it presents your consolidated inventory. First, notice that some of the inventory slots have a colored aura. This is an option where you can highlight the inventory item with the color of it’s rarity. To see a sidebar of all your bags, just click the left-pointing arrow in the top left corner. If you click one of the bags, then all the inventory slots belonging to that bag are highlighted in white. Notice your keyring icon just to the left of “Amanna’s Bags”. Your menu gives you lots of useful options for how to display bags, and sizing and display options for the frame itself. You can control the scale of the window, the number of columns, the opacity, all colors and lots of other settings.
So this is what you see if you click one of your bags to open it, or when you talk to a vendor to buy something. If you’re at the bank, you get a similar window, just with only your bank contents.
OneBag remembers your bank inventory. This is useful for the OneView mini-map icon. Once you visit the bank you can click the OneView icon 
and you’ll get a 
consolidated inventory UI presenting both bank and bag inventory. Notice there are arrow buttons at the top of both your bank inventory and your bag inventory. Click either of these to hide the display of that particular inventory. Click again to expand the inventory. The Config Menu button brings up basically the same configuration screen as OneBag, this one just includes additional options for all bags. The Char Select button lets you choose which of your characters to see the OneView inventory of. Yes, this thing remembers all your characters. I figured that out when I was playing my level 25 Hunter and clicked OneView only to see Scourgestones and Scarabs. The current character name will always be at the top.
I had some mis-starts with this add-on. Some of the buttons didn’t to seem to work like they should. However, now that I have it setup and have played with it for a couple days, it works like a charm with absolutely no issues. This is one add-on that will most likely quickly become a “must have” for both of my characters.
What I like about OneBag
* One consolidated inventory window
* Lots of options to help visually manage your inventory (like the rarity color borders)
* Lots of control over how the window is displayed
* Includes bank and keyring
* Well-integrated into gameplay
What bugs me about OneBag
* Nit-picking here, but look to the left. In the OneView window, your starting backpack is not displayed. The items in it are, but it isn’t. May be my config issue, it just bothers me that it isn’t there.
* Unless it’s an option I haven’t found yet, my keyring doesn’t display in the OneView window.
All in all, OneBag is definitely recommended.
If inventory/bag/item enhancement mods are your thing, check out wowinterface’s Ace: Inventory/Item Enhancement (incl. bags/bank) category listing. Personally, about the only other thing there that I might try out is Fizzle for some durability numbers on my items in character view.
I’m slowly getting acclimated to Bongos, an action bar configuration tool. Once I get a little more up to speed, it will be my next featured add-on.
