What is UMPC?

UMPC is the abbreviation for Utra-Mobile PC. It usually refer to a category of mobile computer in which its size (form factor) is much smaller than a normal notebook PC but much bigger than any mobile phones (smartphone, PDA phone) and PDA.
The form factor was actually proposed in a project called Origami, a joint development by Microsoft, Intel, Samsung and others. Their initial plan only includes tablet PC. Until now, many types of design under this form factor are also considered as UMPC. Let's look at some of the types:

Tablet type UMPC (initial intent of project Origami):

Popular one: Samsung Q1/ Q1 Ultra; others: BenQ S6, etc

Slider type UMPC

Popular one: LG XNote B831, Sony UX490n, Gigabyte MID M528, etc

Notebook type UMPC

Many are under this category: Asus EeePC, MSI wind, Acer AspireOne, Dell Inspiron Mini, Kohjinsha SX3, HP Mininote, Lenovo IdeaPad, etc

Why buying one like this (UMPC) and which one to choose? I will talk about it in later post.