Electricals:
Short answer is it will probably be OK unless the wiring is dodgy (or old) or you already have more appliances than a typical household. Or you are using heaters or air-conditioners that aren't on their own circuit.
The limit for an ordinary household power point is 10 Amp. At 240V, that will be a
maximum of 2400 Watts. Depending on the nature of the appliances being used, under some circumstances 10 Amp will be considerably less than 2400 Watts due to them having a power factor below 1 (that's getting more technical than you need to worry about though
).
Bottom line is most consumer type combination ovens draw about 8 amps and certainly no more than 10. So no problem with overloading the power point as long as you don't use a double adaptor or power board and plug other high usage appliances into the same power point.
The other issue relates to how your house is wired. You will typically have two (or more) power circuits, each rated at 16 or 20 Amp. Typically one for all the power points at one end of the house, the other for the other half of the house. Ideally (and it is good wiring procedure to do so) the kitchen should be split across both circuits since it is a location of high usage - some power points on one, some on others.
The potential issue is simply this. If the oven is drawing 8 amps (for example) then that only leaves 8 - 12 amps on that circuit for everything else. If you have a dryer (8 - 10 amps) also on that circuit and then decide to plug in the George Foreman grill (10 amps) all at the same time then you'll trip a circuit breaker or blow a fuse. No big deal but annoying if it happens all the time.
Easy way to check is just turn off the circuit you'll be plugging the oven into (at the switchboard - turn off the breaker or take the fuse out) and see what else is on the same circuit (that is, which power points don't have power). No problem unless there is more than one big appliance - dryers, heaters, air-conditioner etc on the same circuit AND you will be using them at the same time as the oven. Vacuums use quite a lot too.
Fridges and washing machines don't use much despite their physical size so don't worry about them (except washing machines that heat their own water - they use a lot of power). Also don't worry about TV's (including normal sized plasmas 42" etc), DVD's, computers etc as they don't use much. Likewise don't worry about amplifiers, sound equipment etc if it's normal household stuff.
Realistically though, the bottom line is that you
shouldn't have any electrical issues with these ovens unless either (1) the house is more than 30 years old and has never had a wiring upgrade or (2) you are running plug-in heaters or air-conditioners that have not had a separate circuit installed. 9 times out of 10 if there's a problem of this sort then there's a portable heater involved - they are usually a full 10 amps.
Oven functionality:
Should be fine with the higher end ones (Sharp, Panasonic) etc as long as you're happy with the size and not having a separate oven and microwave.
I have a cheap combination oven. It's more useful than an ordinary microwave but not big enough as a replacement for a conventional oven. Cooks fine however.
For conventional non-microwave cookers, the dual fuel "Emilia" one that I have is tops. 4 gas burners on top, electric oven and grill with 5 cooking modes. Not huge, about the same size as a standard stove, but cooks very well.