The first quarter of Sony's new fiscal year (Apr-Jun 2008) has proved to be quite successful for the PlayStation brand. The gaming division posted a profit of $51 million, a stark change from PS3 loss-driven quarters in the past. PSP played a significant role in bringing PlayStation to profitability, with increasing hardware and software sales.
During this period, PSP sold 3.72 million units worldwide. This is an increase of 75% over Q1 2008. Software sales went up to 11.8 million units, an increase of 20%. While improving software sales is a good sign, this total still trails significant earnings from both the PS2 and PS3.
PSP has been meeting incredible success all over the world, especially in Japan. With sales the way they are now, there's little reason to believe the trend will change any time soon.