Yes, beware! Allow you to monitor your power usage they would, but there are a few things to remember if you're looking at having one installed:
1. Not all smart meters are compatible with other power companies' technology.
Bit of a problem if you want to change power companies, eh?
Also, if you were to get a smart meter, then change power companies, the new power company might not have smart meter technology, so you'd have to go back to estimates.
2. You may have been undercharged (and they'll want back pay!)
To be fair, if you were undercharged, you should pay up - but it's hard to feel any sympathy for the power companies, isn't it? Just be aware that you could be lumped with an amount you hadn't bargained for.
3. Be wary of dangerous CRS (Contractor-Related Shoddiness).
Remember, this is stuff to do with electricity, so the last thing you want is someone doing a shoddy job! If you have a reliable electrician, and you're a bit wary of the job done by the contractor installing the meter, get your man to have a look at it.
For anyone that has changed over, or is thinking of it, know that you can lay complaints with the Electricity & Gas Complaints Commissioner.
So, now I'm sounding like a complete gainsayer; but I'm not against installing a smart meter, since you can monitor your power usage pretty accurately - which is superb if you want to know what you should turn off or use less of.
Just saying, weigh up the costs.