Meetings are fixed events that work well in something like Outlook (so you should definitely use it for that). But for planning an entire day, hour by hour, it's hard to plan in Outlook, and making small changes is very difficult when every item / event is steadfastly fixed, even though you don't particularly care about when it happens.

In short, Outlook is great for keeping track of fixed events and appointments, and Timeslot would be great for planning the things you need to do in a given day, hour by hour.

I'm surprised I haven't had an answer to this. I thought I was the target market.

This looks like an inferior web based edition of Exchange/Outlook functionality. It was a serious question - is there an advantage to using this? If not, you might need to do some market research to better target the problem you are trying to solve.