Heres the Dell setup:
1 back exhaust fan that doubles as a CPU fan at 120mm, decent air flow.  It is inaudible, quieter than the Panaflo.
1 forward intake fan, not sure of the size as I cannot see it.  I think its either a 92mm or an 80mm, it too is inaudible.
1 power supply fan, probably 80mm, it is inaudible also.
For some reason people think that large OEMs use crap or tier2 components.  However, those 3 fans are above the quality of the Panaflo, probably even beating Pabst fans.  They are inaudible (except if you listen real hard on a silent night) and move a decent amount of air.  The heatsink on the CPU (Northwood 1.8) looks to be of pretty high quality too, definitely above that of an Intel retail heatsink.  It appears to be aluminum (not sure of the base plate material) with a lot of fins.  The CPU definitely runs hotter than my 1.6a@2.4.  I guesstimate it to be rougly 50-60C at load.
As for the lifespan, well they offer a 3 year on site warranty.  So it sure better last for 3 years 

  Besides, it'd be bad for their reputation of their computer died after 5 or so years.