What if I can't update OTA? I have wi-fi only. Is JB a performance enhancement, or just new features?
You'll be able to update. I don't have Jelly Bean yet either (I'm in the USA, but some of Europe has it already) but I've had updates to 4.0 through wi-fi. You may have to check for updates to get it in your system settings. Some of Europe already got their Jelly Bean update.
The differences that are apparent ate mentioned in this review:
Ice Cream Sandwich Versus Jelly Bean: The Dish on Android OS
From what I've read, the biggest difference is speed. And there's mention also "Google Now" which I've looked for to add to my ICE Galaxy Tab but I can't find it. It may be that you have to have Jelly Bean to see it in the app store, but I'm not sure.
The following are just some things you can do to customize your tablet, including one to make it look more like Jelly Bean.
You can get some Jelly Bean like enhancements now by searching for them. There's a JB keyboard that you can get now, for example. I prefer Perfect Keyboard Pro, but you may prefer a different one. I like the ability to get to directional arrows to move my cursor back, up, down, etc.
Here's one recommended in a review. It's like the JB keyboard:
https://play.google.com/store/apps/details?id=jellybeankeyboard.f.g&hl=en
And you don't need to wait for Google Now. You can get many features of that voice assistant in Eva Virtual Assistant (or Evan, if you prefer a male voice). That costs a whopping $10 USD, and it's more useful in android phones, because many of its features are set up for reading your text messages, adding entries in your calendar, etc., but you can make use of some of those in your tablet, too. You can also add different voices, like British, Australian, and others, and even a better US voice (less computer-y) than the stock one Google offers.
http://www.bulletproof.com/
EVA Documentation
https://play.google.com/store/apps/developer?id=SVOX+Mobile+Voices&hl=en
Trial version:
https://play.google.com/store/apps/details?id=com.bulletproof.voicerec.intern&hl=en
Not everyone likes the voice assistants, any of them. There are a few free ones, but none of them are as deeply integrated into Android as Eva is. We'll have to see about Google Now. The free voice assistants I've tried were not that great. ALL of them, including Eva, will misunderstand you some of the time. If you have a strange voice, they all might have difficulty with it. Enunciate clearly but don't exaggerate your enunciation.
Some of the free voice assistants will not only misunderstand you, but will reply about things that not only have nothing to do with what you asked about, it will talk about things wouldn't be appropriate in a mixed or business setting. I once asked Iris something about the distance to the moon and she said something like "He certainly has the market cornered on penis size!" I don't use language like that with my tablet, and rarely in any case, so that was entirely unexpected in an office setting. Needless to say Iris is no longer on my tablet.
If you don't like the Touch Wiz desktop Samsung sticks you with, try some different desktop launchers. Many like Nova Launcher, and there's also a "Prime" version, which I have. You only see what you need to see on your desktops, and the app drawer (it has a bunch of dots in a circle on the icon) has all of your apps listed in alphabetical order. You can switch back to Touch Wiz in your system settings if you prefer. If you don't switch to one or the other, you will have to select which desktop launcher you want to use each time you restart. It has almost all 5 star reviews.
Nova Launcher
https://play.google.com/store/apps/details?id=com.teslacoilsw.launcher
Donald
