Plug or core aeration is critical to healthy grass. Spike aerating can actually compact soil even further, and does nothing to break up the thatch layer present on most lawns.
Plugs will be scattered about the lawn and can look a bit odd.
The plugs will usually take 2 weeks to disappear, so the week before your big annual summer party is not the best time to schedule an aeration.
Core aeration is $50 an hour
A standard 5000 ft2 lawn will take roughly an hour to core aerate.
Here it is up close, plugs pulled.