The advantage of good digital thermostats is that they can learn. They'll have the weird swing for a couple of days or so, but if everything is set up correctly (type of heating plant, fuel, etc), after a very short period it becomes dead accurate, because the thermostat learns how long your home takes to heat from a certain temperature to hit the target.
Once it knows that, it will turn on just a tad bit before it's needed and run for exactly the right amount of time to bring it up to temp and turn off even if the temp has not been reached yet, because it knows how much heat the boiler/furnace will continue to add to the space.
I once installed one (Honeywell Magicstat, if I remember right) in a 60-ish year old home with very little insulation and an oil furnace that used 1 gallon of oil per hour. The first month it used 300 gallons of oil. I installed the magicstat, and 3 days later instead of the nearly 10 degree swing the house stayed at a constant 70F and used about 250 gallons/month for the rest of the several winters I've spent there.
Maybe it doesn't fit everyone's style or needs, but our household was very happy with the comfort and economy -- then again, that was back when oil cost a dollar per gallon or less. We moved out 6 months before the price of oil doubled, the new tenants were not happy. They also lowered the thermostat to around 50 degrees, but the walls were so badly insulated that the pipes burst all over the home. Apparently the landlord had to gut and insulate everything.
Cheers,
-- Paulo.