This is one of the few cards in the deck that literally do not speak to me (I believe I could get some chatter out of even the Moon and the Tower, but not this one).
It stumps me as well because I am not sure wether it comes up for good or bad (lucky for me I do not encounter it often). A wheel reminds me of movement, but it could move in any direction, even backwards, for all I know! The four Archangels do not have a very beatific meaning for me, and the other 3 figures are not specially reassuring, either. One is the enigmatic sphinx with the sword of truth and the blue of the Air Suit about it. Then there is a demon and a serpent, far from desirable, the way I see it.
So all I can usually tell when this comes up is that things will get a move on, and hope the other cards tell us what direction the movement takes. If it comes up upside down, I think we are trying to prevent any kind of movement and that things will be stagnant for a while, but that there is a necessary change pending that we will have to face sooner or later.
It all depends on the reading, but I find this card even more enigmatic than the High Priestess. Maybe I relate better to a central human figure.
The first image from the Chinese deck depicts the Feng Shui Bagua with the 8 directions and their respective associations deriving from the I Ching. The four animals are the red phoenix (our front or south), the green or blue dragon (our left or east), the white tiger (our right or west) and the black turtle (back or north). Because I am familiar with this system, it means more to me than the RW's Wheel. It would mean our luck varies depending on its source, so we should be ready to make the most of favorable winds while protecting ourselves from the harsher ones.
Robin Wood's seems to speak about our mood swings, rather than objective causes for them. But I suppose it could mean that we will sometimes have cause for happiness and sometimes pain, and learning to live with the swings as they come.
Spiral's depicts the three ages from mythology and the astrological wheel, so seems to deal more with the time aspect and the fact that nothing is eternal but moving in life cycles.