This is a very interesting thread, and brings out a lot of really great points.
As Jake said, there are different levels of regattas, and managing handicaps should be taken as seriously (or not) as the level of regatta. But, you run the risk of alienating anyone who does take it seriously when you start to bend rules. Finding the right balance, and setting the expectation/tone (communication!!!) is the key.
If we move to a new system, or even just start seeing more handicap racing, it will put more emphasis on getting the ratings right before racing. Unless you have a dedicated volunteer (or team), don't expect much to happen on Saturday morning of a weekend regatta, in terms of settling numbers.
But, we've all been to regattas where someone has clearly been allowed to break a class rule, just to get the regatta numbers up. Whether racing OD or handicap, this is not a problem if handled well (communicate well with the legal boat owners, and don't start letting the whole thing turn into frankenboats over time), and as long as the illegal boats don't win.