Like someone else said, I really (even after many years of reading translations and listening to people like Peter Goldsbury) have only a little idea of what Ueshiba Sensei would say about this topic. I let that little idea influence some of my own perspectives...but hey, he wasn't god, I don't worship him, and I have to find my own way, any how. I have had experiences like Erick's, though, and have also struggled with the "beast within". I guess for me, there are a few issues here as well...
Desire...I often see as the "I want" voice in my head. I want a new car, I want to make more money, I want a beautiful, sexy girlfriend who does all the things that turn me on. I think it occured to me several years ago that the "I want" voice needs to be strictly controlled, and that the desires it goes after are not always the best things for me. Some of that figuring out came through aikido, a lot of it did not.
Power...comes in many forms, shapes sizes. Words can have power, ideas can have power, objects can have power, people can have power. On top of that, there are different types of power. Physical power, spiritual power, etc. Sometimes power is used negatively, sometimes positively. Too many variations for me to be concerned with all of them.
For me, if there is are kinds of power that I seek, some would be the power to influence others without being physical (words, sounds, actions that do not encroach on physical bounderies). Or the power to sustain an assualt, absorb the power directed toward me, and then transmit that power back into a person. Or even to establish my own physical power in a situation that demands it.
So I don't see a neccesarily negative or positive connotation for the word power. If I am doing judo, a nice powerfull sweep is just fine. If I am trying to isolate the power behind a particular aikido throw, I may want to look at power a little differently. It really becomes an "it depends" situation...and those "it depends" situations require constant vigilence.
Aiki...I tend to think of more and more as a set of physical skills which may, or may not, lead someone to what may also be something more than the physical skills. YMMV.
So I tend to be carefull about the "I Want" where power is concerned...just because of the nature of the "I Want" and the nature of power. And if I apply those things to Aiki, again, I think being vigilent about your own integrity is paramount. If you lose that integrity, even for a moment, there may be a very high price to pay.
But then, very few things worth doing are easy, right?