Re:UPS...
They are quoting the standard Laptop battery (Lithium Ion I assume) as a UPS, yet I've seen that with most batteries of this kind that continuous charging actually slowly breaks the battery causing it to store a lower charge, therefore not lasting anything as long as it's supposed to. So after a few months of use the UPS becomes pretty useless...
Or is that only on the really crappy & cheap Dell ones?
This is actually more of a design issue. Traditionally Dell laptops power up via the battery hence you can not remove the battery when the machine is on mains power. Hence Dell batteries have in my experience tended to run slightly warm even when the machine is on mains.
Most other laptops settle for a augmented supply configuration where the battery is an either/or option and gets charged via the mains when it is available. To me this latter configuration makes most sense for a UPS as a UPS should be able to handle a brown out as well as a conventional blackout.
However you do get problems with batteries when you cycle frequently my current laptop needed a new battery after 9 months of being power cycled twice a day but then most people don't need to work on a train for a stupid number of hours a day.