Okay, bit of beta-testing to report here:
First, system specs:
Video card: Dual NVIDIA GeForce 7800 GT's, running in SLI mode.
Sound: Realtek 97 Audio.
System: Windows XP Home edition Version 2002, Service Pack 2.
CPU: AMD Athlon 64 X2 Dual Core Processor 3800+
2.01 GHz, 2.00 GB of RAM.
First, a bunch of alt-tabbing to see how well the game handled it.
Alt-tabbing while the ironclad company intro was playing caused looping sound briefly and some system stuttering, but this was a brief effect and the alt-tab was successful.
Alt-tabbing from the title screen and in-game sometimes caused the game music to continue playing in the background for a few seconds, but after waiting awhile the music stopped.
During the game, returning from an alt-tab would sometimes cause an odd black horizontal line to flash on the screen briefly. This would only happen once for about a tenth of a second, and then the game would have no more errors.
In ALL cases I'm happy to report that game worked just fine after being alt-tabbed - in fact, I've got it alt-tabbed right now. It's even happy with me playing winamp in the background.
While playing the first tutorial mission, I accidentally sent my scout frigates ahead to the battle and left my capital ship behind. When the scout frigates had won, the game claimed that my capital ship had level up when it had not. Furthermore, I was then forced to select an ability to proceed through the tutorial. Fortunately I was able to simply purchase a level-up for the ship, and proceeded that way.
Later, in the battle around the enemy planet, I used the ion bolt ability on the enemy's gauss defense platform. When I did so, the capital ship instantly switched to another target (The naval factory), which certainly isn't what I wanted it to do while that gauss platform still existed.
Finally, I noticed severe screen flickering whenever I went back to the main menu, either from a tutorial or from a sub-menu.
Thanks for making such a great game - keep it up! Hope this helps somewhat.