Summary:My results are good. I am an electrical engineer and also followed all the directions. The booster's transmitter could afford to be about 2-3dB stronger. Still, my goal of making my GSM (T-Mobile) phone useful inside my house was well achieved with some minor effort.Detail:I purchased my YX500-PCS for use with my T-Mobile Blackberry Pearl 8100 in Saratoga, CA. I live in a one story, 2400 sf, ranch style home with a metal roofing system called "Calpac" that uses formed and coated sheet metal panels to simulate a tile roof. The house structure is wood framing with wood siding on the front side and stucco on the other three. I mention this because this means that my house is at least partially shielded by metal on top and on the three stucco sides (remember that stucco is hung on steel mesh). If you have a similar home, you should seriously consider placing the remote antenna of the YX500 outside of your house and not in the attic as others have done. You don't want to have metal between the antenna and the cell tower.Before the YX500, I could not reliably connect to my T-Mobile service inside my home. At best, I could get one bar near certain windows. I could get satisfactory reception by taking my phone outside and seeking out a "line of sight" path to the cell tower. After installing the unit with my antenna attached to the chimney on my TV antenna mast, I can use my phone pretty much throughout my home. Placement of the base station is more sensitive than I would have liked to see. The issue is that it's transmission strength is usable, but weaker than I would have liked to see. My expectation was that I would be 3/5 bars as a minimum, and the reality is that I lose a bar ever ten or so feet. This is mostly OK since I get 5 bars when close to the unit (within 10 feet). So, you must make sure it is centrally located and that your principle location in the house (say, your desk or office) does not cause the booster to be on the other side of the funrnace/AC (if you have central HVAC), water heater, etc. Remember, avoid metal, especially grounded metal, objects. They absorb or block the radio waves you are trying to receive. In any case, I temporarily set up the antenna and the unit as recommended in the instructions and moved the components around to get the best signal strength on my phone's meter. One of the reviewers commented that he "can't see radio waves" and neither can I. We can all MEASURE them, however, and that is what we are doing in a crude way with our cell phone signal strength meter.In any case, I ended up installing my antenna outside on my TV antenna mast. In general, higher up should be better to avoid the obstruction of buildings, etc. You should check the location of the nearest tower that serves your area and your carrier. There are websites that can help with this (e.g. www.cellreception.com/towers/) or you can simply contact your carrier directly. Once you know your nearest tower location, you should locate your antenna so that there is as much of a clear view as you can achieve to that site. Of course, a totally clear view may not be possible. You should try to avoid metal structures, concrete stuctures (they have metal reinforcements), etc. Trees and vegetation should be less of a problem. Some wood frame houses will block reception and some won't. It depends on what is inside and if they have some hidden metal like mine has.In any case, your goal is to get the strongest signal to the outside antenna you can, because the YX500 is a signal booster or amplifier. It follows that if you have no reception when you climb up a ladder or onto your roof outside with cell phone in hand, you will not fix anything with a booster because there is nothing to amplify or "boost." Conversely, if you get the antenna positioned to receive the strongest signal from the tower or cell base site, you will also get the strongest signal and best results inside the house, too. To put it another way, this unit "captures" the best signal you can find with the external antenna and then sends it into your home via the cable it is attached to. The base unit then re-issues that signal back out through its antenna as well as receiving your cell phone's signal and sending it the other way. The signal inside your house is not going to be better than the one that is initially captured outside. If you only had one bar of reception and it was scratchy when standing at a high spot outside with your phone, you are going to just get a somewhat more powerful, but similarly distorted signal once you install the booster.In any case, after installing and testing this unit for goodness with my Pearl, my son's friends came over armed with a bunch of ATT (Cingular) phones which are all GSM. Previously, these did not work at my house, but now they all do. This might not be that much of a blessing in this specific case :-) but the system has now been tested with two services and the latest RAZR variants on ATT as well as my BBY.Bottom line, do a lot of signal monitoring with your cell to see if you can even use this device. If you decide it's a go, follow all the instructions and you should be fine.