We drilled holes in the back for a while too, but one of the selling points was that they're "virtually waterproof" and the holes had a negative impact on that. (I worked for a Micros dealership when they first came out and we poured a cup of water over one just like in the sales video and the thing really did keep working.)
One of the biggest problems with overheating is the staff throwing stuff on the workstations. When I started my current job the eclipses were blowing out almost weekly. There were check presenters, menus, napkins, etc... piled on and around the workstations, leaving no room for air to circulate. We started holding the managers responsible and issuing a kind of demerit against their bonuses whenever this happened. We have 186 eclipses across all our stores and I don't think we've had more than 10 calls total for overheated workstations in the 3 years since that policy was put in place.