AT&T is planning on launching their LTE network later this year, and they want to do it in a big way – as big as HTC’s upcoming 4.5″ qHD phone called Holiday. The phone will also have a dual core 1.2 Ghz Snapdragon CPU, just like the one in HTC Sensation. It will also come with 1GB of memory, an 8 MP rear camera (with LED flash), a 1.3 megapixel front-facing camera, 802.11b/g/n WiFi and Bluetooth 3.0. It will run Android 2.3.4 and the Sense 3.0 UI on top.

The HTC Holiday does seem to be a little different than what HTC has released so far, without so many rounded corners, but more like a slab, that looks like a piece of chocolate on the back. I’m not entirely sure why all manufacturers seems to be moving to 4.5″ displays, though. I do realize that with screens being such an important part of our smartphones these days, we want to maximize the viewing space on the device, but isn’t 4.5″ pushing it a little too far for most people?

At first I thought these 4.5″ phones would have the buttons included in the user interface, the way they are implemented in Honeycomb, so basically even if a display was 4.6″-4.7″ with the buttons included, the phone sporting that would still be about as big as a current 4.3″ one. But it looks like they are making the display for the UI 4.5″, and then there’s another portion for the buttons, too, which makes the phone even bigger. At what point does the phone become too big to be maneuvered with just one hand? For example, I like to drop down the notification bar with the thumb from the same hand holding the phone. Would I still be able to do that with a 4.5″ phone? Probably not, or not as quickly and easily.

I don’t mind them experimenting with different sizes. In fact I wish they experimented with the 11.6″ tablet sizes as well, and with a 4:3 form factor, but I assume they still want these devices to sell in volume, not just to a small niche market with very large hands. At this point, I’m hoping Nexus Prime with its rumored 4.65″ display, will actually have the buttons included in the interface somehow. A display that large with an HD resolution should be beautiful, but it should be compact enough to still be usable with one hand.