I have bought a Samsung Galaxy TAB 2 recently, and its rather neat. I have the 7 inch version, which is big enough for what I want to use it for. However, the full size 10 inch is just as good but a bit more expensive.
Its important to know what you will be using it for. If it is going to be the only, or main PC that you own, then a 10 inch is the one to go for. Using a tablet is not the same as using a proper PC however, and you will need to get used to it. Typing on a on-screen keyboard isn't the most satisfying experience for instance, but if you do find yourself typing away with gay abandon, then a 10 inch would be preferable to a 7 inch.
Also bear in mind that the majority of tablets don't have many ports like USB to use, unlike a proper PC. So if you use a memory stick on a regular basis, a tablet won't be as easy . And if you intend to connect to a larger screen or your TV...again not as simple as a PC.
But if you want something that is easy, very quick start-up time and very portable, and you intend to use it for surfing, or playing games, or keeping up with emails, then a tablet would make sense. I spent 3 hours in Terminal Three at Heathrow last Friday, waiting for my nephew to get in from Australia, and the Samsung was a god send. No Guardian available at 05.00 AM !
The Samsung 7 inch is being sold at Tesco for £158, with £30 cashback from Samsung. Now this has to be good value for money by anybodies standard.
You will notice I haven't mentioned Apple. They make some very good tablets but, just like their regular computers, they are twice the price of any other on the market. I can't see that the new mini ipad is any better than my Samsung, and its over twice the cost.
I wouldn't get bogged down with operating systems by the way. The Android seems just as good as Windows, and a lot more stable if my experience these last few weeks are anything to go by.