Just got home after a wonderful 5 day trip in MP. We started in Cusco and visited many of the ruins sites in the area before heading up to MP. Our trip was organized by EcoAmerica Tours out of Texas and they did a wonderful job. We always had someone to meet us at the airports, hotels and tours. They truly took out the hassle of travel. This is not a lay around type of vacation. We were on the go from early morning till late each evening. I would also not recommend this type of travel with small children.
At the moment, if you are staying in Cusco you need to travel by bus for just over an hour to catch the train to MP. The train ride is then about 2 hours (this was the dome train). They offer some lite snacks on the train and it is all clean and well appointed. As far as we can tell they will not be changing the bus/train thing anytime soon.
A guide met us at the front of MP (you can also hire one when you get there). It is also very easy to get around and walk MP by yourself. But if you want to learn about what you are seeing then you should have a guide. Very insightful.
Walking around MP requires a lot of stair climbing on rocky paths. If you are not steady on your feet it is best to take it slowly. But it is doable for everyone and I saw people in wheelchairs as well.
As suggested by many on these forums it is great if you can spend the night in A. C. You then have the chance to see the ruins in either the morning or the afternoon without the large crowds. About 2000 people per day visit the site but most are gone by 3:30 in the afternoon and don't arrive again until after 10am.
If you have it in you, try to climb towards or to the Sun gate as it gives you another perspective. The walk is steep but the view is worth it.
We stayed at Hatun Inti and I have posted a review. Great little hotel. Indio Feliz is an even better restaurant.
However if you want really great views then book ahead and climb Wayna Picchu. You will not get in if you try to go on the day without tickets. If you read anything about the place you know they only allow 200 people at 7am and then again at 10am. We took the 10am trip up and it was not too hot. We were lucky and had great weather on both days. Lots of sunshine but not hot.
Again this is a fairly tough climb but very doable. The steps are very steep at the top. Just take your time and it can be done. We were never bothered by altitude.
If anyone has questions I would be happy to answer. Hope everyone going has a great trip.