The McCarran airport slots are known to be notoriously tight-fisted when it comes to payouts, which is why many people in the know avoid these slots like the plague. Only tourists arriving in Vegas and those who have money burning a hole in their pocket play these machines. Occasionally you do get a machine that pays off good, but those are few and far between.
If you've got time to kill and like to watch planes taking off and landing, McCarran does have a dedicated parking area for plane spotting. It's on Sunset Road just east of the 215 spur going into the airport. Landings are generally on the shorter of the two runways (7R/25L), while takeoffs are on the longer (14,000'+) 7L/25R. There are two north-south runways, 1L/19R and 1R/19L; these are used mostly by general and corporate aviation traffic, flights heading up to Reno or Southern California (mainly by Southwest) and a peculiar private airline going to a certain destination that doesn't officially exist on any map!