1. Instead of putting CSS in the plugin create a reference (class?) so that the style can be referenced and maintained in the theme Style.CSS file (other plugins do this). Maybe you could make this an option to allow for both or at very least make it an expandable text box...it is very hard to work with all the css in the tiny area provided.
2. Also more control (Styling) over the text fields would be good (location, price, time etc)
3. Location should really be Title or Event
4. A separate entry should be added for Address/Location
The label With: should be optional or modifiable so you can have no label or say something like Details or Description to describe the event etc. (I had to remove it from the php and changed the label in the setup page to Notes.)
5. You should consider allowing for multiple dates or a date range in case a band is appearing at an event consecutive days.
6. Allow for different date & time formats ...or default to the date & time format selected in Settings>General>Date Format of WordPress.
7. (Low Priority) Would be really nice if optionally you could have the plugin get the google map for the address and display it (it can insert a link/button... so the map displays in a separate tab or window when the link/button is clicked) (I use one of the buttons in the plugin to do this now but have to get the map url and paste etc. not a big deal but for musicians it would be simpler if done for them)
8. (Lowest Priority) Option to automatically create a separate page or post for the gig (so it can be pointed to via a URL Link)