The PRST1 has the standard Sony Original 3-font set (serif, sans-serif, monospace), just like previous models, plus 3 serifs (Amasis, Palatino nova, Really No2) plus 3 sans-serifs (Frutiger Neue, Univers Next, Verdana).
The 3 serifs are all better to read with (IMO) than the Original serif. Unfortunately if you select any of the 6 'specials' it seems totally random whether the bold and/or italic text in your book will be rendered as such. Some will be some won't. There's even a note in the User Guide admitting the problem.
Note
When you select other than the [Original] font, boldface/italics/italicized boldface may not be displayed correctly.
The only way I've been able to use my own fonts is to physically embed them in the epub. There is also a cautionary note about doing this but so far I haven't experienced a problem. Time will tell.
Note
The font size and font of some content with embedded fonts may not change.
Here's a link to a summary I did in another thread. I am somewhat surprised there haven't been more new T1 owners commenting on this problem. Perhaps most people don't mind if italics go AWOL.