I agree with Icho. Lemmings isn't really a game for hints, but rather for experimenting with the various skills in different ways to find the solution, and using hints would ruin the whole experience of playing the game.
Having easy access to hints, and even just having hints at all, will encourage players to take the easy way out of solving a level: not having to work for the solution. In the extreme, this could lead to lazy players and diminishing interest in the game because such players will get accustomed to using hints to solve levels and will skip those levels which require thinking and effort. Additionally, players experimenting with levels leads to the discovery of bugs, new tricks, etc., meaning that the amount of those things found will decrease if usage of hints comes into being and increases.
If you really want to have hints for a level pack, including a text document with the download shouldn't be that much trouble, especially for namida and Nepster because they won't have to include a hint feature.
I feel that a text document is a better way of giving the player hints as it isn't readily available and requires that the player does more than just press a key, mitigating the possible negative effects aforementioned.
Personally, I won't use hints if they are added. If I really want to know the solution to the level, I'll just find a replay or check youtube.