@Sunglasses_Ron check the website mate as when I looked the train was fully booked until Aug 7th!!! It was my backup plan for getting down if I was spent after the walk up. You also have to prebook parking for the Miners track - it was full when I got there, didnt know that either so I had to do the Llanberis route.
I went yesterday (solo), made the summit in 2hrs 26m - never sweated so much. Was dripping off me. For the "easy" route it was pretty hard going.
Total round trip was 3h31m moving time with about 40min added for breaks and a sandwich at the top. My legs are ruined today. Ankles, calves, knees, quads, hips... walking like a 90 year old!
Views - absolutely epic.
Edit - if you have a dicey knee I wouldnt recommend walking up, its hard going up but on the way down your knees take a right beating.
Edit2 - If you decide to go anyway, take a warm top for high up, take a couple of litres of fluids each, and some food. There is one small cafe at 4km, no toilets. Round trip from Llanberis car park was 15.05km. The path is jagged and stony for a fair portion, & VERY steep in places.