Are cycling shoes comfortable as everyday wear?
Unless you're using clipless pedals, you really don't need much in terms of special shoes for cycling.  However, there are plenty of advantages to using clipless pedals,  so many people choose to use them.  

The big categories of clipless shoes are:
Road shoes tend to have the cleat exposed and you walk on it any time you step. This is really bad for regular wear off the bike. These shoes are meant to be lite and used on the bike.

Mountain Bike Shoes tend to allow you to walk around a bit.  Some models resemble athletic shoes and some are more firm and the stiff soles make it hard to walk normally. However, you can usually get buy walking a bit in these.  I wouldn't want to wear them for extended periods of time off the bike if possible. 

Urban Shoes (like Chrome and DZR) tend to look like sneakers and feel a lot more like regular shoes.  They still contain a cleat mount, but these shoes are designed to blend in like normal shoes and walk a bit better than most other cycling shoes.  I've worn Chrome and DZR shoes with SPD cleats around all day and didn't really notice much.  The soles are still stiff, so they are a bit different feeling than wakling around in regular shoes. 

If you pick up a pair of clipless shoes, you'll still probably want to swap them out for regular shoes at the office if you're going to be there for a few hours or more.  Regular shoes are going to be more comfortable and your cycling shoes might be a bit sweaty.

If you're not planning to pick up clipless shoes, then look for a pair of athletic shoes that doesn't have a lot of flex in the sole when you try to bend the toe downward. A flatter type of tread on the bottom of the shoe will probably help keep you from sliding on the pedals as much too.  Skateboard shoes and Adidas Sambas are generally pretty good choices, but pick what works for you.  

If your commute is short, you can always try your regular office shoes. They may not be 'optimal' for cycling, but you don't always have to have specialized gear to ride a bike. Do what works and what you're comfortable with.