Autorouters will only do what you tell them. These beasts are 100% rules driven. The time is in the rules definition as regardless of what it says on the box, some rules regarding grids or 'channels' will conflict with other rules such as grid settings vs trace width settings, clearance, net length matching, diff pairs, clock from toos & termination and so on.
Sometimes the time to set up the rules is more than the time to route manually especially if you have a lot of mixed analogue/digital rules to follow and use split planes.
If you use software for capture that will translate all PCB rules defined at SCH level to be followed by router then you will save time. Protel does not do this, or at least does not allow for proper rules definition in SCH yet with enough parameters to work on a dense design.
For a mid range router, well integrated into the tool suite Pads is pretty hard to beat with Blaze.
Specctra is really cool but I have not seen it work well with other tools, based on quality of rules translation and interactivity level, outside of Cadence suites. But no suprise there of course
The Specctra interface is where most non-cadence tools fall down, but I beleive PCAD works very well with it as they used Specctra for many years anyway.
All down to time, and in some cases available CPU time & lots of RAM!
Howver most routers can help in routing some of the sh#t work like fanout, memory arrays or reptative routing and so on. Even the cheap built in ones do this OK most of the time.
As regard PC motherboards routing, the last project I was involved with long time ago was a team effort and they used Specctra, based on a Pentium Pro CPU, the time allocated for defining and optimising the rules, of which most can be obtained from most vendors or associated standrads anyway, was 6 months!
Cheaper to buy a mobo these days
:R