All the current ACT products offer instant status, and actually, they offer the fastest instant status. Levition has status reporting, but its not as fast as ACT. With ACT an association is set up between the switch and the device (or HomeSeer). When you control the switch, a command is sent instantly. The command is routed, so its not limited in range. This feature is available in all their 103, 153, and 120 switches, as well as the lamp and appliance modules. If a lamp module is controlled with another controller (say a handheld remote), it will send a command to an associated device (or HomeSeer).
Some other features to consider are programmable ramp rates for dimming. ACT, Leviton, and Monster support this (ACT supports an almost infinite range, while the Leviton/Monster support 8 rates). Intermatic does not support this in either of their lines, a big omission in my opinion) I am not sure about Cooper.
The ACT switches require wire nuts as they use flying leads (can be tough to fit in some boxes). Leviton/Monster use screw terminals, very nice.
Levtion/Monster support 3-way or more operation with all devices. This is good and bad. It means you have to buy a $100 switch for all locations. ACT requires a different switch for use in 3-way and 4-way installations, but the slave switch is a special switch and is low cost. Only 2 slaves are supported however. More slaves may be added using other swtiches as transmitters and associating them with the load controlling switch.
Hope this clears things up a bit.
-Rich
HomeSeer Technologies LLC