Pursuing the benefits of human stem cell cloning does not preclude the abandonment of other types of therapeutic cloning treatments. If adult rat brain cells provide a treatment currently, then by all means, it should be pursued with haste. However, let me remind you that the pursuit of that method also could have unintended consequences as it is still in development.
As to your charge of stem cell research being open ended with no projected time-line for success, I can only remind you of two other projects that share the same status:
The Future of the Space Program which is costing
16.8 Billion for 2007 The Human Genome Project for which analysis is still on-going with its last reported expenditure of $437 million.
Further, there have been successes in therapeutic human cloning. The time-line of cloning in general has produced a major success nearly every two years since 1952 with the experiments of Briggs and King, to the discovery of the DNA model by Watson and Crick, all the way up to the current cloning of human tissues on rat cells as you mentioned. All of these are steps towards a greater breakthrough.
As to your assertion that embryo's used for research would develop into human beings, I can only point you to the fact that currently, there are no restrictions on the destruction of human embryo's anyway. In fact, abortion is quite legal and serves no more purpose than a convenience. Reproductive therapies involving the use of fertilized embryos accounts for the destruction of thousands of embryos every year. These byproducts of "acceptable" treatment could be put to the use of creating new stem cell lines.
Finally, there are processes by which embryonic stem cell lines can be produced
without ever destroying the embryo, thereby eliminating any reasonable moral objection to the cloning of human stem cell lines.
Basically, there is no excuse not to lift the bans on creating these stem cell lines considering the potential gain. As with all research, it is a process that takes time and resources. The only moral objection has been overcome so all we are left with is hysteria and misinformation as opposition to a valuable tool that can save millions eventually.