Hello! I'm 41 - congratulations and welcome to the over-40s club :)
There are a quite a few of us around and I know of two 47 year olds that had surprise babies who are both doing well and very happy, now that they have got over the shock!
Everyone's different, but for me personally, I've been fit and well, and age alone hasn't affected me so far (although this is my first so can only compare to my family and friends). You will probably get referred to a consultant as a matter of course, due to age alone (due to an increased risk of problems for the baby's health and outcome of the pregnancy) and you may get offered extra scans as a result but if all's going well, it doesn't necessarily change your options regarding childbirth.
In terms of energy, I'm in the 3rd trimester now and starting to feel tired if I over-do things, but I'm flat out in a stressful job, still traveling, have 3 step children on the go and a load of commitments outside work. Fortunately my job is flexible but I'm expecting something to need to slip soon. But this is no different from friends of mine, 10 years younger, in a similar situation.
In my case, I can only say it's been positive so far. My partner is very supportive and the children are massively excited about the new baby and I'm looking forward to having baby-sitting on-tap in a couple of years time 
It's a tough decision however and different for every woman. There is no right or wrong answer, but I hope the above helps.