Some early notes:

1) The new skins look good, and the overall level and quantity of content is good value for the price of the expansion pack.

2) The campaign map has not changed from the early pics that were shown here, and is still very "blobby". However it is quite large and has many provinces and cities, once you get used to the strangely liquid look, it actually is quite pleasing

3) Battles seem exactly like RTW, with one VERY annoying exception, a change to the camera controls. In normal RTW, when you double click on the unit card of a unit you want to zoom to (say because they are on the other side of the field), and you don't want to wait for the camera to finish its pan, you can just flick the mouse pointer to the side of the screen and the camera jumps instantly to the unit you needed to see. Now, with Alexander, doing this stops the camera pan dead, and returns the camera to its previous position! So now it takes much longer to zoom to a unit which isn't in your field of vision, which isn't good given the extremely fast pace of RTW battles.

4) Don't want to see the immersion-killing "100 years remaining"? Simply comment out the line "show_date_as_turns_remaining" in the game's descr_strat file.

5) Persia can be made playable simply by moving its entry in the descr_strat file, as with regular RTW. Not tried the other states.

6) The campaign so far is quite challenging compared to regular, am looking forward to getting into it.

7) RTW: Alexander reports itself as version 1.9, so it looks like there is going to be a patch to bring RTW up to 1.7 and BI up to 1.8. Should fix the siege tower bug I guess.