Personally, I think the key thing(s) when looking to buy something like a tablet, is to get something firm in terms of expectation and use. If you have a good idea of what you plan to use it for, and also a consideration that your initial thoughts or ideas on that may evolve as you may find that such a device becomes more useful, the more you've had chance to use it.
When I bought the android tablet I've got, I had some firm ideas of what I wanted to use it for - video playback: both offline (ie from local storage) and online using things like iPlayer and catch-up TV sites; light web surfing, email usage; ebook reading (ideally the Kindle app) - and that's about it, for me - not really that interested in games, not truly that interested in their being a wild gamut of apps, either. One other android app I've made good use of, being a free internet radio app (tunein I think it's called).
So with one of my main interests being video playback, local storage, plus expandability were important, plus the hardware chipset in terms of video performance.
Reasonably well performing battery life and a reasonably sized and performing screen were also key factors to me.
Things I decided weren't important: camera(s), GPS chipset, 3G connectivity. I'm still happy with that - although the more I use portable gadgets like this, and Kindle, I'm seeing more the benefit of 3G connectivity - especially the type of 3G support and capabilities that were included in the Kindle keyboard 3G version.
I bought a "budget" Android tablet - it cost me around £150, had a decent chipset (Tegra 2), 10.something size screen, that performs quite well, decent resolution, decent on-board storage (16G), expandable (microsdhc slot). There's no camera(s), no GPS chipset, and as stock, didn't come with google market / play.
Although no previous experience with Android as an OS / software, learning how to make use of new (to me) software and devices, has been something of a requirement in my working life, so getting up to speed with Android, including rooting and installing / configuring custom roms / firmware wasn't too daunting for me.
I have to say, I've had great value and made a lot of use of my tablet in the time I've had it. Stability and performance have been key to me, so it's running pretty much stock software (tapntap / 2.2 / froyo build) slightly modified (rooted, with google market / play installed). And I have to say I've been delighted with it, in terms of how it performs, and the value I get out of it as a device.
Looking at the tablet John has linked to, I have to say, the feedback looks good, the device looks reasonably capable (has 1GB RAM which is a good start), and is running an up-to-date OS / rom / firmware (ICS), and has google market / play installed. That all sounds good, because out of the box, you'll probably find no true need to immediately install a different rom, because as stock it's up-to-date, and having market / play there, you won't have to start tinkering at the outset to get access. What will be key, though, is what you plan and can reasonably expect you want to use and get out of a tablet.
As to the spend a bit more and get product X - I'm not immune from those arguments - several family members have current iPads, with varying degrees of use out of them. Personally, they're not for me, seem too restrictive, don't provide enough reasonably priced options for local storage - but I also recognise that there is something to them in terms of their simplicity and user interface.
I get that some will say "Buy cheap, buy twice..." and I don't wholly disagree - there are some devices at the cheaper end of the market that will likely fail and disappoint - but reviews, research and consideration as to spec can mitigate all that. With more prestigious tablet devices in my close family, I suspect I get the most - or at least as much - use with my budget android tablet, compared with the more proprietary, prestigious devices - and as such I've been delighted with the value and use I've realised from my £150 android tablet.
If you choose wisely, and are happy to tinker a little bit, and depending on requirements they can make a good option. If you want things more simple, perhaps unconcerned with the restrictions or value for money, things like iPads can be worth their notably higher price tag.
edit: one other tip I have, from an Android perspective, anyways - plenty of people tinker, experiment with various different roms / firmware - I did at first - but doing so can see you constantly tweaking, fixing, and researching issues - and for some, that's part of the experience. But there's something to be said for speed and stability, and rock-solid configuration. So whereas I played around for a good while with various different firmware / roms for a while (some of that was because the initial stock rom was so bad for the tablet I had), but over time, the current stock rom for my device is vastly improved in terms of performance and stability. Such that I've stayed with that (albeit, slightly modified) for quite a while now, and whilst it may not be the most modern incarnation of Android, it truly is rock-solid, and performs excellently - and along that line, various roms seem quite sensitive to the version of flash installed (10.3.something.or.other seems to be the golden version) just be wary of updating flash, if it currently works well - even if other websites mither about upgrading it.
