HP business class laptops - ProBooks and Elitebooks.  8000-series.

Unlike consumer models, they have replaceable parts that you can get to if you take the covers off the sides and back.  They are made of aluminum, so if you drop it, you have just put a dent in your wood floor, and your laptop does not explode or break.  These things are made to run 24/7 in a business server environment for 5+ years.

Buy last year's model off of HP's website in December for a discount.  Or get a refurb online.

Get a docking station for your desk/monitors/keyboard/mouse - instant desktop experience.  But you can pick it up and carry it into the other room.  They aren't light, but they are cheap/hr to operate, and reliable.  The 2000-series are the light ones for road warriors, and they perform, but they are crazy expensive.

Mac, IMHO, is not a business laptop.  They are a premium consumer lifestyle machine unless you are working in a narrow range of graphics processing, and I haven't kept up for a while, but I'm assuming the 64-bit architecture of Win7 has closed that gap.  Most actual business software (software utilities to upgrade your GPS equipment, GIS software to interact with your precision data, almost any specialty software) is PC-based.

How do you use Excel (Office 365) less than once a year?  I use it daily.  Lots of times/day.  $90 for 5 workstations is <$1/month/machine.  LibreOffice is a choice you can get by with, if you don't need the business functions of Excel that business people who exchange files daily and write macros that need to be exchangeable need.

I'm actually a little shocked that iOS and the iPad (and I love my reliable iPad) has been so successful and that the business world has adapted to cloud-based data that someone else charges you monthly to provide.  What a wonderful way to extract economic rents.  I would have figured the usability of a Microsoft Surface (have never used one), in that it has a keyboard and USB functionality, would have eventually won out in the business world, but it seems to have gone the way of the Zune (Zoon? - I don't even remember that far back).