Electric resistance heat is a great long-term solution for the electric power supplier; it's usually one of the most expensive heat options for the homeowner to run, barring power subsidies or absurdly cheap power, which happens a few places, but not many. The details will be local, so you'll have to investigate the relative costs of the heat sources you have available. If you have natural gas, I'd be very surprised if electric didn't cost you 3-4 times as much to run, for instance.
In general, you are not only going to need new wires to rooms, you may need upgraded electrical service to the house. Start with "what is the BTU/Hr output of your furnace" and you can work back to kilowatts and amperes required for equivalent heat output.
3412.14 BTU/hr=1 kilowatt. 1 therm (100,000 BTU) = 29.3 KWh (if gas heater was 100% efficient) or that number multiplied by the furnace efficiency (ie, 93% high-eff furnace, 1 therm = 27.25 KWh) - fill in your local prices and furnace efficiency and you'll have a quick idea what it will cost you. For my electric cost of 15 cents/KWh, a therm would have to cost $4.08 to be equivalent to electric - while a therm around here actually costs about $1.48 - unfortunately I don't have a gas line on my road.
Hydronic radiant can be retrofit - options vary depending on construction details, and how much of the house you intend to rip apart - but you'll be similarly inconvenienced to install electric radiant, so that may be a wash.
If you have concrete floors that are not adequately insulated from the ground, radiant may never work right for those floors.
In some cases it may make more sense to install radiant in the walls or ceiling.