Personally, I find using my Lumie Body Clocks (yes plural) really helps me get up in the winter.
A number of my friends were keen on the idea but wanted to try out the idea of a light alarm before they paid more than £50 for one. A few of them therefore tried this iPhone app that gives you a feel of how even a small amount of light in the morning can help: http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=346542660
The light is nowhere near as bright as a Lumie lamp, but for a cheap price it gives you an idea of how much light can help wake you up in the morning. I used the the iPhone app above and then went on to buy 2 Lumie lights cos I loved the difference a light in the morning makes :-)
The Lumie lights are far better than the iPhone app above, but for under a pound it gives you a good idea of just how much it can make getting up in the morning more pleasant.
The other point to remember is that if you buy from Lumie, they offer a 30 day trial period. There's a restocking fee of £15, though. Personally I prefer to use a dawn simulator that plugs into a separate lamp, as I found the Bodyclock wasn't bright enough to read by. You can also haunt eBay for second-hand ones, but be careful, as there are some truly nasty cheaper dawn simulators on there. Brands like Sunrise System, Apollo and Philips are fine.