I think mixed reviews cover 2 models, the TH1212 and TH1212B
Customer Rating: 
I don't know for sure but the majority of negative reviews are older and the majority of positive reviews are newer and Panasonic did upgrade the model somewhere along the line from TH1212 to TH1212B. My experience with this product over the last month+ has been very good, both my Motorola and my wife's Kyocera connected with ease. One feature I really like is that when I leave my cell phone about twice the distance from the base unit than they recommend (which I do often) and a call comes in the Panasonic simply boosts the signal strength after about 10 seconds into the call to compensate for the weak connection and the call becomes clear. I've had no dropped calls and the Panasonic actually does a better job than my cell on duplexing (both people talking at the same time).
The only complaint I have is that the unit doesn't access the cell phones phone-book so you have to re-enter everything into the Panasonic that is already in your cell phone.
The peace of mind knowing that we'll get any emergency calls without having to remember to take our cell phones to bed with us is worth every penny as our parents are getting older and our teens, that only recently got their licenses, are staying out later.
BTW, I had been looking at this type of product for about a year before I bought it this one for $70 a month ago and felt it was a deal, now at $55 it's hard to go wrong.
Not compatible with 1st generation iPhone.
Customer Rating: I like Panasonic phones and tried hard to get this system to work for my setup. I wanted to use this as a landline replacement in conjunction with my original series iPhone. If you look through the positive and negative product reviews, you will notice that users of the newer iPhones (at least the 3Gs model) seemed to have good luck with the Panasonic system. On the other hand, if you look at the compatible phone list on panasonic.com you'll simply see "iPhone" listed--without regard to the various generations of the iPhone.
The problem for me was that outgoing calls work fine, but almost all incoming calls are cut-off if I use the Panasonic handset to pick up the call. The problem was also visible in making the Bluetooth connection: I reset the Panasonic unit and also used the deregistration process to deregister the iPhone. And I also used the "Forget this Device" feature on the iPhone, to be sure I was erasing the connection on each device. I even did a full reset and restore on the iPhone. What I noted was that, when trying the initial pairing, the iPhone would repeatedly find but not connect with the Panasonic. (You could enter the Pin code, but not get to the "Connected" status.) It did eventually connect, but then resulted in dropped call situation noted above.
After talking extensively with both Apple and Panasonic tech support, and after locating a "Supported Bluetooth Profiles" chart (modified August 2009) on apple.com, I now think the problem has to do with the fact that the first generation iPhone only supported the HFP (Hands-Free Profile), and not any of the more advanced profiles, such as A2DP. The iPhone does use Bluetooth 2.0, which should work, but doesn't in this case. The iPhone Bluetooth itself is fine--it still unpairs and re-pairs with my Jawbone, for example. And the Panasonic unit itself works fine: My old Motorola RAZR (V3xx) works like a charm with the Link to Cell. But the iPhone and the Link to Cell just won't play well together.
The newer iPhones use Bluetooth 2.1 + edr, which, according to the Bluetooth website, includes faster data transfer between devices. That might account for the positive reviews by people with the iPhone 3Gs (and probably the 3G model as well).
In summary, the product description should reflect the fact that first generation iPhones do not appear to be compatible. In contrast, see my review of the VTech DS 6322. The VTech which works seamlessly with the "old" iPhone, even though--again--the only supposed requirement is Bluetooth 2.0, just like the Panasonic.
