Great work!
Alot of attempts have been made to produce good RTS games for flash. Especially those that play like conventional RTS games, but with an easily accessible flash interface. The success rate of these attempts aren't very high sometimes, but this is one solid piece of work.
I can see the influence, and being a Huge CnC fan myself, I absolutely adore this game. It's very well made, very clean and polished and sticks too good solid RTS gameplay.
A little thought though, have you by any chance played the game 'Battlegrounds' ? There are some control advantages in there that could make this game even better.
For one, I think the inability to overlap units is kind of a sharp blow. This means I can't horde my units together and they automatically form a straight line. If it is necessary to know how many units are in a particular 'overlap' you could easily add a unit counter everytime a group is selected. Also, some kind of keyboard group mapping would be really nice if you could add that feature.
The other thing I think this thing needs a little bit is a deselect button. It may not be entirely necessary but I think in a flash context, it helps the selecting of units and buildings around the map.
This game does play very closely to CnC and I think it's going in a great direction. I was actually hoping that the building menu would be similar with the 2 columns for units and buildings always accessible at all times and there would be no need for selecting a particular building to build something. I don't even know how possible that is within the realms of flash, but if it could be done it would be extremely cool.
This thing is a pretty fantastic piece of work. I have a feeling it could become quite a flash sensation.