Yes, the desktop version may have this limitation.
But, why can't anyone just tell us which hardware components we could use to achieve the high resolutions?! Provided that 99% of the laptops use these cheap, resolution-unbalanced displays, we should be able to alleviate this somehow?!

Oh, Kostadin, please sorry me for being such an ignorant person. I read the GMA 4500 specifications sheet and I was pretty sure that Intel won't say anything which can be interpreted dually. I can't believe that manufacturer of computer is able to limit the output resolution of integrated graphics. I mean of course it's possible, he just need to use a specific controller to ouput the video signal, but I don't understand why wouldn't he choose the maximum supported by GPU...

Sorry again. "Век живи, век учись".

For the sake of 'telling the full story', here's a discussion at some intel forum:
http://communities.intel.com/message/176417
But, I am more open to trust the fully-detailed explanation from dell's forum!

No, you are not correct. The limitations are imposed by the implementation. Read the longest post from here: http://en.community.dell.com/support-forums/peripherals/f/3529/p/19483304/20264148.aspx
The cable that I tried is from HAMA(German manufacturer, I think) and was labeled as "high speed hdmi with ethernet, 4096х2160 capable". There is no HDMI-version(1.1, .1.2, 1.3 or 1.4) on the package, although advertized 1.3. I guess that might mean that it doesn't provide the high resolutions part of the standard, but, anyway, this whole thing got so loathy and loose... But, I won't use the words that are coming to my mind at the moment...
The bad thing is that the notebook, that I currently plan to upgrade to(the Samsung X300C), is again equipped only with HDMI.

Kostadin, you are limited by your graphics adapter: Intel® Graphics Media Accelerator (GMA) 4500MHD can only provide 1920 x 1080 resolution while being connected via HDMI cable. If you buy any modern notebook PC you'll be able to use the full resolution of your external screen. It doesn't matter which one graphics card to choose, whether it would be NVIDIA GeForce GT 635M or AMD Radeon HD 7670M (for example). They can output 2560 x 1600 pixels via digital connection.

Sorry for poor English.

Hello. I am fond of these form-factor laptops and now using one Timeline 3810. I wanted to upgrade my external monitor to a 27-inch(2560x1440) one. I went to a store to look at one dell model with that resolution - the U2713H. I was limited to using the HDMI, I had some suspicions that it won't load the native resolution. And it couldn't - it only ran at full-hd(1920x1080). I, then, researched and it seems that HDMI implementation across OS-drivers, GPUs, cables and even the monitors themselves(providing EDID-data) may impose such limitations.

So, as I like that particular model that you reviewed, I'd like to ask you try hooking it to one extended-resolution(2560x1440) display over some good HDMI 1.4 cable. That way those of us who need to combine the cutting-edge portability with the great desktop experience that these extended-resolution monitors provide, could clear-out the options available.

Kostadin