This is probably a simple answer for many of you.... but is it a hassle-free endeavor to have two CS4 installations and alternate activations for usage?

Taking an extended work trip, and it would be nice to be able to do some post work on the laptop.

With Adobe, you get two activations (per license, one for your desktop and one for your laptop). I've had no trouble with that.

I have not tried having installations on more than two machines, but can't see any reason why it would be a problem as long as you de-activate the installations you're not using so that at any given time, you have no more than two activations in effect.

That's great info Pete...thank you.

You get one activation for desktop and one for laptop??? I didn't know that! I used to have my CS3 Master Collection installed on my desktop, then needed it on my laptop so tried installing it there but it wouldn't let me activate it till I had de-activated my desktop. Is this a new feature to CS4, or is it on CS3 as well? If it is on CS3, how do I activate both? I'd LOVE to have it on both my desktop and my laptop...

No, not a new feature. Maybe you accidentally burned up one of your activations with a system change/update or something but you should have two activations. Here is the EULA page:

Adobe - Adobe product license agreements (http://www.adobe.com/products/eulas/)

The PPro CS4 license is multi-lingual and the US English version starts on page 123 of the PDF. The paragraph you'll be interested in is 2.4 on page 124. I currently have two installations of CS4, one on a laptop and one on my main editing box and had no problem at all with installing and using them. If you aren't being allowed the second activation, you may need to contact Adobe (and let us know how that goes).

My second activation worked perfectly (my cynical side feels as though it's the best feature of CS4, but it's downhill from there).

Thanks again Pete.

Hmm... I'm pretty sure I remember to deactivate it every time I uninstalled it, but I'll try it again. If it throws me an error, I'll go ahead and contact Adobe and see what I can work out. I've gotta re-install my OS on my desktop anyway, so I think I'm going to try Windows 7...