[Przemolog]

Some European voice in discussion (however, neither French or Italian) .

Originally Posted by KarenM

I sign up for a UM account with the Lichtenstein #.

I then sign up w/CBW for an 800 number. (in my case, I'd pay the $1.50 for no pin.)

At that point, my phone number changes from whatever UM gave me (Lichtenstein #) to a U.S. 800 number. Correct? And, anyone calling me from within Europe would also use the 800 #?

As Matha has already told, you don't "lose" or "change" your phone number.
In fact, you have two phone numbers. The first one is a Liechtenstein number assigned to the UM SIM card (ie. a piece of electronics which you'll receive from the vendor and insert in an appropriate place in your mobile phone). If someone calls that number, and you're in Europe, you pay nothing for receiving a call. A 800 "personal" number from CBW is completely independent of UM or any other operator.

Originally Posted by KarenM

I master the callback procedures as described above.

When I call to Italy# from within Italy, or to France# within France, I have to use the country code without the first zero, as if I were making the call from the U.S.?

GSM mobile phones and networks support "international number format". This means that no matter where you are and where you are calling/messaging, you dial +CountryCodeDestinationNumber , eg. +12345556789 for US/Canada,
+391234567890 for Italy etc. If you mean "leading zero" used for national calls within some countries, you'right - if you replace this zero with +CountryCode, it'll be OK. Usually you dial "+" sign just by long pressing a key on the phone with "+" printed on it.

Originally Posted by KarenM

HOWEVER, do I understand that IF the Yackie system is working correctly, it would replace BOTH the UM and CBW, while also providing a U.S. based, permanent, phone number?

From the technical point of view you're right. Moreover, Yackie also offer non-US landline numbers. It's not clearly stated on their website if it is possible, but at least in theory you might have more than one number attached to same the mobile phone e.g from US, France and Italy...
The problem with Yackie is that you pay for all received calls, and so far the balance check and topping up the account is possible only via the website. Thus, you're risking running out of the credit, especially when you don't have frequent access to internet. With CBW's 800 # used to forwarding your calls there's no such a risk since it's a postpaid service - your credit card will be charged after calls, you don't have to make an advance payment(prepaid).

Originally Posted by KarenM

3. Can receive messages??

If by "messages" you mean "text messages" aka SMS, you can receive them for free. It doesn't matter if you choose an "international" SIM card like UM, or SIM cards from national operators in France and Italy. But of course, you must remember some facts:
1) No matter if you use CBW or any service of that kind (i.e. with a US number forwarded to a mobile phone number in another country), text messages must be sent to the mobile phone number assigned to your SIM card, not to the US number. This rule applies to UM and to national SIM cards from France, Italy or any other country as well.
Yackie SIM cards use Israeli numbers for SMS sending/receiving.
2) Basically you can make a voice call from any country to any other country in the world. But international SMS interchange is generally possible only between networks which signed so-called roaming agreements. Even in that case, messages don't need to go through e.g. in this thread Matha told that he couldn't send messages from T-Mobile USA to UM (despite there's a roaming agreement between T-Mo and FL1, the "real world" operator of UM).
3) If you want to have messages sent to your mobile phone as e-mails (e.g. to 423663012345@united-mobile.com), forget it! Since receiving messages in Europe is free, such e-mail2sms forwarding is very rare, since neither sender nor "addressee" would pay for such a service .