Another plus is that you have a head of vacuum to provide instant grip when vacuum clamping, you can clamp and release and clamp again as fast as you like because only the vacuum in the lines need to replaced between cycles and as you have a vacuum control switch monitoring the reserve, the available vacuum remains constant. This also mean that the pump itself only needs to run when the reservoir requires topping up, saving wear and tear and reducing shop noise.
Speaking of wear and tear, the system includes a mac valve, (the small blue box on my system) which works in conjunction with a check valve (inline brass fitting) and a small 'free air' tank (the small red cylinder on my system). These components work together to save a great deal of load on the vacuum pump when it needs to restart each time the Hg drops by providing 'free air' which is air at normal atmospheric pressure, thereby allowing the pump to reach full speed instantly instead of fighting against any vacuum which remains in reserve.
So these fancy looking systems do actually have a function over and above a standard vacuum pump with direct connection to the work piece insomuch that they make working with vacuum more reliable and efficient. They reduce wear on the vacuum pump. They increase the flexibility of the tool and they reduce noise and power consumption.
So there

P.S. Jeff, I believe many people use the old fridge motors with 'suckcess'. If you go down this track just be aware that not all are equal. Newer pumps are designed for better insulated fridges so are designed to run less frequently. You are better with an older style pump as they are designed to run for longer periods before they over heat and burn out. The newer pumps do have circuity to avoid over heating, but this needs to be bypassed for them to work as vacuum pumps and once you do that, they suffer a much shorter life span. That said, the older motors avoid heat by carrying more cooling oil, and this in itself can bring it's own issues for obvious reasons.
P.S.S. Since i took the above image i have also added a set of 2" swiveling casters to the underside of the unit as it is quite hefty little sucker. I have also added a cord caddy to the "T" clamp which hold the reservoirs in place.
Here is where i got my swiveling casters, $7.80 a set of 4 plus $11 express post to my door. Good casters and good service.
http://stores.shop.ebay.com.au/C-TOOLS- ... QQ_fsubZ12
Cheers
Kim