It's not a desktop CPU. It's a mobile CPU and those tend to have lower TDP compared to desktop models. Those probably use Ultrabook-class processors with 17W TDP (oh, 7W Haswell, wherefore art thou?). Intel has been able to lower their idle power consumption significantly so typical power consumption for Ivy Bridge tablets will probably be less than 10W. By the way, I haven't had any issues with my Sandy Bridge and Ivy Bridge laptops in sleep mode. Also, iirc, my Sandy Bridge laptops sit at around 7-8W while doing typical tasks such as web browsing, etc and those have normal 35W TDP mobile processors (will have to re-confirm this with the Kill-A-Watt).
For you, perhaps. For me, the extra performance will be well worth the price assuming I can get at least 4 hours battery life and cooling/thermal design is decent. Before the iPad, $1,500~3,000 was the going price for tablets so I'm not particularly bothered by a $1,500 price tag as long as it's able to deliver. I'd rather pay extra for snappy performance than deal with all the CPU limitations of an Atom-based tablet (yes, I use an SSD for OS drive on all my systems). While I don't require the level of performance the i5-3317U can deliver, the problem is that Atom is still just too slow for me. With the Atom, my computer freezes for several minutes if I just even connect my e-reader to the netbook (granted, the e-reader does have a couple of thousand ebooks in it). I can usually bring the Atom to a crawl with my web browsing habits (around 20 windows with 50+ tabs each).
One nice thing about the Transformer Book is it'll also double as replacement laptop (assuming you don't need a high performance laptop). With the dock, you get even longer battery life. Probably way better compared to your typical Ultrabook.