I've had mine for almost 2 weeks now. I also have the BB PlayBook, and a Transformer. The 8.9" size is perfect I think. It's so light and comfortable to hold. The only issue I've had is the browser crashing on some sites, but switching to Dolphin HD helped.
Like @Shempster, I'm looking for a thin case and I can't find one. I don't want to bulk the tablet up. There are a couple cases on Amazon, but I really like to see/feel a case before I buy it. For now I just keep it in a zippered netbook sleeve.
I like TouchWiz on it. All the screens, even the Settings screen, looks nice. They add colors and icons that really make Honeycomb look good. I'm normally prefer a plain vanilla experience, but I really like this.
The BB PlayBook is really nice too I must admit. It is rock solid, and so portable. Not many apps for it yet, but it will run Android apps shortly. If you have a BB phone, you can bridge it to the PlayBook and get Internet access on it from your phone. No need to buy an extra hotspot plan. I probably use the 8.9 70%, and the PlayBook 30%. The PlayBook travels with me wherever I go because of it's size. Gorilla glass gives me confidence that the screen isn't going to scratch as easy too. And it makes a nice Pandora radio while driving.
Batter life is great on the 8.9. It feels solid and well built. The thinness takes some getting used to. At first it felt slippery, and I feared dropping it. But I can actually grip the thing in portrait mode. But it's that thinness, and lightness that really makes this a nice device.
The price is a little high I think. And they really need to put a SD slot in these. I hate to say it but it reminds me of Apple. They want you to buy a more expensive device just to get more memory. Makes no sense, especially when you see cheaper tablets full of expansion slots.
And it still runs 3.2. I had a Fascinate, and we all know Samsung is notorious for not getting updates out in a timely manner. There are no carries involved, so I'm not sure why they can't get 3.2 rolling. My guess is it's probably TouchWiz holding it up, but who knows.