Lots of topics here, but to address the one about having a retirement plan at all. Our clients tend to have money in their plan because their employer has set it up for them. Those same people and many others just don't have money in their own pocket to invest, probably because it is too easy to access. Having a plan enforces discipline for savings and prevents you from spending with out tax consequence.
Secondly, moving money around in the plan without tax consequences is easier in a plan. For example some of our clients as they get older and particularly in this market, don't want to tie up their funds in real estate long term, but elect to be lenders. So they have their Self-Directed IRA sell the RE and they then make loans back to the buyer via seller financing. They also provide loans to others secured by Real Estate.
Depends on your own personal goals and situation, but I think most people benefit from having a tax sheltered plan.
Our clients at NewDirectionIRA take advantage of all the options for investing. Recently more of them have been having their IRA obtain bank financing for property.