I agree with all the comments above. I use an aircraft for business and am in no doubt it can provide a very good alternative means of travel. The comments about the weather are of course valid, although it is surprising that for most the year, I guess more especially in the South, how rare it is to be unable to fly. From personal view there is however little doubt that you first need to accumulate a reasonable amount of experience. When a new or newish PPL we all know there were many occasions when you would not safely conduct a flight because of the weather conditions with which you can cope perfectly well with more experience. Obviously an IMC or IR opens up the horizons even further, however that presupposes a suitable "mount" is available. As has been commented on before it is one thing to use an aircraft for occasional IMC use when conditions are benign, quite another when bases are at or around minimum and icing is a real threat. The shortness of the day and the often early closing times of airports in the winter should also not be overlooked. A night rating may help of course.
All that said there are two far more practical observations to be made. Firstly it can be falsely assumed travel by air will save time! Be very careful. Think about the time to get to the airport, the time to get the plane ready, delays at the hold, time to park and secure the aircraft at the other end, and MOST important, time and the means to get from the airport to where ever you are going. It is an interesting equation. I reckon that anywhere in the UK to which you can fly that is within an hours fly distance for me it will be much quicker to go car. Around an hour and a half it becomes marginal, particularly if the place being visited is very close to the airport (but be careful, this is usually not the case). Beyond that it starts to become quicker, but then I am reasonably close to my home airfield. Of course if the trip involves a short sea crossing the time advantages swing rapidly in favour of flying. For example a trip to the I of W by car is a time consuming event, but pretty painless by air. The advantages are even greater for the north of France and beyond, although again, and I don’t speak from personal experience, there will be a point beyond at which a commercial carrier will present a far better alternative.
The second observation is aircraft reliability. Cars rarely develop tec. faults that prevent you completing the journey, but who wants to fly on one mag.? Technical problems arise and with far greater frequency on some aircraft that on others.
In short, for business use think carefully about how close your client / customer is to the airport and how you will get to him, how much time you really will save and what the fall back is, if the weather is unkind or the aircraft develops a tec problem. Having thought about all that go and enjoy, or change jobs so that all your clients / customers are based on airfields around the country and you can afford to fly a twin a get yourself an IMC or IR rating.
Seriously on a positive I go to Oxford on business for example. For me, including all the time spent on preparation, I reckon it saves me at least three hours on the round trip, and sometimes a lot more thanks to the usual M25 congestion. I have not yet had to cancel a trip (summer and winter) but I am able to be flexible when I go, and rarely plan a visit more than a day in advance.
The most important factor I have left until last. When it all works it is of course enormously satisfying, and with a little experience I find far more relaxing than driving. The added bonus is that the Revenue are of course not concerned with whether a particular journey has costs you ten times as much as going my Shankseys pony, so go ahead and deduct the whole cost and enjoy!