Having read some of the comments and bugs I thought it might be useful to add some clarification on a couple of terms.

What we have released so far is only the regular weight of the font.
Fonts – in general – come in many weights from ultra-light to ultra-bold. The fact that regular is the only weight that is complete so far, means that when you look at items that are set to be bold in the Ubuntu Beta font your computer is guessing at how best to display the font bold. Bold is coming as are other weights and variants such as monospace, italics, etc.

Monospace is primarily used in the terminal and in applications such as xchat. The regular which is available now, is not going to work as well as the monospace if you use it in the terminal or in xchat etc.

This regular weight is fully hinted and kerned for Latin, Greek and Cyrillic so there is still plenty to try out.

Hinting is the process of telling your computer what to do with the individual pixels that make up a glyph. Wikipedia has a detailed explanation (of course).

Kerning is the process of defining how much space there should be between individual glyphs (characters). And here is the wikipedia information on kerning .

For those of you who know all this – excellent!
For those of you who don’t – I do hope this helps!