Unfortunately, technology buffs are generally wonderfully ignorant about the basic mechanics of space flight; which usually helps them sound very confident in describing everything a technology can & can't do.

VASIMR is basically a SEP-derivative which uses an unbuilt nuclear power source as an energy source; which means that the development of this technology is almost certainly to be measured in the billions (because you have to build both the nuclear power sources & drive mechanisms capable of actually using that level of power; as well as mission architectures - from the buses to the launches systems required to boost these missions safely from Earth - capable of supporting such a bulky thrust system); & you'll have to spend this money at the expense of all of the literally dozens of missions you can fly now without such toys. Based on previous press release technologies which space agencies have spend fortunes on, if VASIMR is porkrolled, the resultant system will inevitably prove to be less flexible than advertised at greater cost (both in terms of technology development & in continuing operationals); so it won't actually help many of the missions currently being proposed for it & the loss/benefit ratio becomes even less.

Please forgive my profound cynicism about your wide eyed expectations; but i'm tired of seeing agencies spending fortunes on over hyped technologies at the expense of real space exploration... & by the way: solar sails can achieve orbital lock quite easily (& indeed just about everything else chemical propulsion can do), albeit sometimes at the expense of time....

Robert