The Mini 12 is basically a mixed bag. Although it offers a vastly superior screen compared to regular netbooks, it still comes up short in some departments.
The 3-cell battery doesn't offer much endurance, and the 1.3GHz Atom would struggle with Windows, and it's not a very impressive performer under Ubuntu either. This is hardly Dell's fault, and many other vendors still opt for the same CPU. Even Acer's new 11.6-inch Aspire One 751 is powered by the Z520. The Mini 12 also lacks storage, 60GB is basically 100GB short of what you're supposed to see on a netbook.
With the shortcomings out of the way, it's obvious the 1280x800 12-inch screen provides you with a lot more comfort than a regular 10-incher. I'd be willing to trade 100GB of storage for 2 inches of screen space anytime, but just 60GB of storage simply won't be enough for many users. The Mini 12 also looks good, it's a very thin, sleek piece of kit. It won't turn heads like a MacBook Air or Dell Adamo, but it's good enough considering the price.
Until a few weeks ago, the Mini 12 was the only Atom based notebook with a decent, 12-inch screen. However, Acer's Aspire One 751 has joined the club, and it offers an 11.6-inch 1366x768 screen, and identical CPU and 2GB of memory, 160GB of storage and XP for just over €400. Some reviewers have blasted its build quality, but since we haven't tried it out yet, we really can't say how it measures up to the Mini 12.
Dell has recently announced it's pulling the Mini 9, and the Mini 12 will probably follow suite soon, and considering Intel's stance on 12-inch netbooks, we might not even see a successor. You can still get it in most markets, with prices starting at about $400. It's a bit cheaper than the Acer, but it's also not as well spec'd as the Acer either.