What a silly question--who still uses Outlook? You might not like it, but millions still do use it! I have mixed feelings about it, but it has plenty of strengths. Your comparisions to Yahoo and Gmail are irrelevant here.
To topic: I strongly support the notion of splitting PSTs. While newer versions of Outlook support larger than 2 GB PST files, I'd be very careful letting them get too big.
Keep Up with TechRepublic