The new Apple iMac design lends itself more towards use as central part of a home entertainment centre, as well as boasting top-end performance. [Review updated November 12, 2009]

The two ultra-high-end 27-inch iMacs are the first to use Intel's Core i5 and Core i7 quad-core processors. The remainder (two 21.5-inch and one 27-inch) use a 3.06GHz Intel Core 2 Duo processor.

Latest (late 2012 models): Apple iMac 21.5-inch review and Apple iMac 27-inch review

iMac screen

The most obvious change in Apple's new all-in-one computer range is to the iMac screen. Both the 21.5- and 27-inch screens are made with high definition video in mind.

And the 27-inch model is, in a word, stunning.

Don't take my word for it. That's based on the cluster of techie-types and graphic designers who popped into my office last week to get a gander at the newest all-in-one Mac from Apple.

Part of it might have been the novelty: Apple unveiled these larger, widescreen iMacs on October 20 and sent one over for review purposes two days later.

It's the biggest change for the iMac since it went aluminium-and-black in late 2007.

Like on many HDTVs, the black border around the new iMac's screen reaches out to the very edge; the aluminium border that surrounded the screen in the previous iMac is gone.

21.5-inch and 27-inch Apple iMac

This gives the effect of the screen being bigger than it really is. To the chagrin of many, there is no matte screen option. Glossy is your only choice.

The glossy effect makes colours pop and blacks deep and rich, but you can see your reflection in the glass.

When using the iMac as a desktop computer, I've learned how to see past the glare and reflections, but many others cannot develop such tolerance - and I'm not saying you should.

Glare is a problem if you're in a group gathered around the 27-inch iMac that's being used as an HDTV. In fact, because of the glare, you might reconsider using the 27-inch iMac as a HDTV.

However, it's now been two years since the first aluminium iMac with glass was introduced, and there are no signs that Apple is interested in offering a matte screen option.

While the 21.5-inch iMac isn't much bigger than the previous 20-inch iMac on paper, sitting side-by-side, the 21.5-inch iMac seems huge. It has a 1,920-x-1,080-pixel resolution.

The 27-inch iMac is gloriously big, but one Macworld editor said it might even be too big as a desktop Mac.

That screen, the largest LED-backlit computer display out there for now, offers a resolution of 2,560-x-1,440 pixels for a true 16:9 aspect ratio. According to Apple, the basic £949 model - and its slightly pricier £1,199 brother - offers 17 percent more pixels than the old 20-inch iterations (16:10 aspect ratio).

That's 90 percent of the screen real estate you'd get from Apple's gargantuan 30-inch Cinema Display and it's perfect for viewing high-definition content.

Judging from the coos of approval I heard when I fired up some hi-def movie trailers for the huddled masses, this iMac should sell well.

In fact, hi-def content is so sharp and bright that it almost looks 3D. The big question you'll be asking yourself is: "Do I put this in an office or show it off in the living room?"

At first glance, you might mistake the new iMacs for HDTVs - in fact, the new 27-inch iMac has support for a VESA Mount Adapter Kit (£20) for mounting on a wall.

Apple says that the iMac screens are LED-backlit widescreen TFT active-matrix LCDs with in-plane switching technology, and can display millions of colours at all resolutions.

Switch on the iMacs, and you'll notice that the LED backlit screens on both the 21.5- and 27-inch models are a bit brighter than their predecessors. Look even closer at the 21.5-inch iMac, and you'll notice that its colors are much better than the 20-inch iMac.

That's because Apple thankfully now uses 8-bit displays across the iMac line - the 6-bit dithered display used in the 20-inch iMac is gone (we hope).

Both of the new displays use in-plane switching (IPS) technology, which is supposed to help maintain image quality when viewing the screen at extreme angles.

Looking at the new iMacs at different angles, I had a difficult time noticing any colour shifting.

When compared side-by-side against the previous iMacs, the 20-inch iMac screen looks like a mess, while the new iMac screens maintained their colour integrity.

NEXT: iMac case design and iMac memory