In reply to ThunderCat:
You don't really need to take dollars anymore, you can pay for your visa at the airport with £, and you can change £ everywhere now, personally I draw cash out at home rather than use my card and am careful with it, cheaper in the long run as long as you don't lose it. If you have pre-arranged a guest house or hotel get them to pick you up from the airport, just tell them your flight number. Otherwise expect to pay 700-1000 nrps, about $7-10 to Thamel from the airport, and expect to be asked to pay $25! If you haven't booked anywhere you can ask the taxi driver you end up with and he will almost certainly take you to a reasonable place and then once there they'll be able to sort you out with whatever else you need to go trekking etc. Nepal is a pretty amenable place just don't take a guide from the street in Thamel.
Make up several passport size photos before you go, easy enough to do on a PC, as you'll need a few: 2 each for the visa, trekking permits, TIMS etc.
Also you'll get given a visa form on the plane in so just try and nip round the people walking to the arrivals hall to get a bit up the queue.
No disadvantages to getting them at the airport. Even with the queue your baggage will still appear long after you are out of that section.
No problems with that time either but Kathmandu does go to bed surprisingly early, not much after 10pm. If there's power shedding going on it will by dark in the streets with generators in the tourist places. Take a headtorch with you. If you are concerned arrange for a pick up as I said and they will turn up when the flight gets in.
Post edited at 22:02