I would not recommend the central vacuum. The suction is nothing compaired to your standard Nilfisk or Dyson vacuum. Also small items get blocked in the pipes which are difficult to remove. I have heard that it can also depend on how far away the motor is from the actual outlets. (the closer the motor the more powerful the vacuum.
Emerb, this is complete nonsense.
Central vacuum systems can be more or less powerful that your standard Nilfisk or Dyson vacuum, it all depends on what size system you install. There are central vacuum systems available that will do a complete hotel, with a number of people vacuuming at once, while others are only suited to a small apartment. In picking the suitable unit for a house you must consider the floor area of the house, and the total distance of piping that will be installed. You can compare the suction strength of different units by comparing the water lift value. The bigger the stronger, it compares the units by showing how far up a specific sized pipe the system can draw a column of water.
Blockages in the system are generally due to poor installation, and are very uncommon if installed correctly. The nozzle on the inlet hose should be narrower that the rest of the pipe work to prevent objects which are too big to travel through the system from entering it. The only problem here is if a long narrow object enters the system. However, this should get caught at the wall inlet as there should be a sharp 90 degree bend behind it to prevent these objects passing into the system. This is the only place where a sharp 90 degree bend should be installed, sweeping 90 degree bends should be used elsewhere. There are many other important points to consider when installing junctions where pipes meet, but any good installer will know about these.
If you do get a blockage, it can generally be removed by sucking it back out through the inlet. Never try to force a blockage further into the system.
You also mention that the further you are from the unit, the weaker the vacuum. This should not be a major problem as since only one inlet is open at a time, a vacuum should form in the rest of the sytem. Again, correctly matching the correct size unit to the particular house is important.
I have diy installed a Beam system. Its very straight forward as long as you follow a few simple principles. However, if you do not understand how the system works, pay the few quid extra and get it installed.