The history of aluminium wiring casted a shadow on its use. I have been opposed to the use of aluminium for those reasons. WIth the high cost of cooper, aluminium is getting to be more attractive to use. Compact aluminium conductors seems to be more common these days. By using compact aluminium provides a more robust cross section when terminating them. With less void between the stands means that is it harded to "smoosh" them They still require TLC and proper torquing to ensure a good, solid connection. Another nice thing with compact aluminium is that the conductors OS diameter is usually smaller then copper. For example, a 3/0 xhhw OS diameter is .72" while a 4/0 compact aluminim is only about .59 This means you should not need to increase the conduit size to allow the use of larger aluminum conductor. I personally will still limit its use but will be warm to the use of aluminium. If you are thinking to use aluminium, do your home work like local codes, be certain that your connectors are "AL" rated, and torque properly.