The Test and Verdict
The IPWS application auto-launches when you boot and runs in the System Tray / Notification area. It has no adjustments for you to fiddle with and uses three different icons to communicate status of Ready, Not Connected or In-Use. But I couldn't tell the difference between the Ready and Not Connected icons and found it easier to just look at the Ready, Regular Call and Internet Call status lights on the front of the IPWS itself.
Skype and the IPWS application communicate as needed to manage Skype and PSTN calls. If for some reason you quit Skype, the IPWS software will launch it when you go to make a call. But I found the IPWS application doesn't wait long enough for Skype to get up and running, so you'll have to hang up and start the call again. I also found that if I quit the IPWS application and then tried to quit Skype, Skype just hung until I killed it from the Windows Task Manager.
Once everything is running, you just hit ## on your telephone keypad, wait for the European-style dial tone and punch in the speed-dial code. Although the IPWS works for both Skype and Skype-Out calls, you can only use speed-dial codes to call Skype network users. You'll have to dial Skype-Out calls as you would on an ordinary phone, but with a 00 or 001 prefix.
The IPWS automatically switches incoming Skype or PSTN calls to the connected phone(s), and even gives you a double ring to indicate a Skype call. Caller ID works fine for PSTN calls, but you get no indication of who is calling on an incoming Skype call. Other nice touches are that you'll get a familiar call-waiting beep if a call comes in on the other line when you're on either a PSTN or Skype call. You use ## to switch between "lines" and if you hang up and forget someone you left holding on the other line, the IPWS will ring you back so that you can complete that call. And when the computer it's connected to is shut off, the IPWS defaults to connecting its Phone and Line jacks together so that you can make and receive PSTN calls.
I made and received a few test calls and enjoyed not getting tangled in the long cord of the headset that I had been using for Skype calls. And I didn't really miss the higher-fidelity of a headset-based Skype call (your typical telephone is not intended to be a high-fidelity instrument), although the difference surprised me at first. I did have one odd occurrence where a Skype caller could hear my wife on a simultaneous PSTN call but I couldn't hear her. I didn't have time to try to reproduce the problem before deadline, but I suspect the problem might have been caused by us both using cordless phones, although I don't know for sure.
If you're a heavy Skype call user and want the convenience of Skyping from the same phone(s) you use for normal calling, the IPWS can be just the ticket. But with a little Googling / Froogling you can find similar products from less-familiar vendors and save $10 - $20 from the $60 or so the IPWS currently goes for. Buffalo Technology and others also have recently announced Skype "partnerships", so even more choices should be available soon.