I took a minibus from Pai to the border where I spent the night before crossing into Lao the next morning. After crossing the border we were driven to the slow boat pier where we boarded a very long, very narrow boat along with about 110 other people for the two day journey down the river.
The seats on the boat are really just car seat benches (like from minivans), and the boat was so crowded and my seat so constricting that I chose instead to spend the day perched on a sack of rice in the living quarters in the back of the boat. It was actually much preferable to being squeezed in up front, and I even got in a brief nap on the floor before one of the boatmen came by to get rice for his food (prepared with river water).
We spent about 6 hours on the boat before pulling into a tiny river town that has nothing but guesthouses for tourists on the slow boat. We had dinner at an Indian restaurant (run by a real Indian!) and then went to bed.
The next day was another 8 hours on the boat before arriving in Luang Prabang.
My first day in LPB I went to the Kuangsi Waterfall. That night everyone went to the bar, and when that closed at 11:30 we went out to the dance club (awkward Laos and awkward Lao music), and once that closed at 12:15 we went bowling (the only place in the city open after midnight).
The next day we took a tuk tuk and ferry to the Pak Ou buddha caves and had an amazing all-you-can-fit-on-your-plate vegetarian dinner for about $1.35. And the following morning I left for Vang Vieng.