Howdy Wargaffer,
I meant to answer some of your questions back in March and didn't. Better late than never, eh?
What is the most important thing for you in a wargame?
Ultimately, the game needs to be fun. If I'm not enjoying my time with the game, than what's the point? However, I don't think that is what you meant. After the fun factor, a wargame should reflect supply, fog of war, and appropriate decision making for the level of command the game is representing.
Do you prefer solo or multiplayer games and why? (for both physical and digital games)
Prefer multiplayer, over solo; however, solo is fine. I enjoy the social aspect of multiplayer, as well as playing against a thinking opponent, or with a thinking teammate, if playing co-op or on a team.
What is the most challenging thing about the hobby?
Time. Too many games, not enough time.
What do you like or dislike about campaigns? (campaigns are a series of scenarios that usually influence each other)
Likes: Decisions made during the campaign influence/impact what happens in the individual scenarios.
Dislikes: People lose interest and the campaign isn't concluded
What do you like or dislike about randomness mechanics in wargames? (activation, movement, dice, cards, random number generators, etc.)
Randomness is good. Limiting the ability of the players to control every aspect of the game is a bonus. Games that allow me to move every piece are fine; however, games that potentially limit what I can move, and when those pieces move, provides a decision making experience that can be more fun and thought provoking than getting to move everything.
Have you ever tried tools to create scenarios? (for example, Memoir44 and C&C have a scenario builder that you can download)
Yes. If the tools or guidelines are clear and well thought out, it is fun. If the tools are not easy to use, or disorganized, that is not good.
Do you like playing custom scenarios or do you prefer playing official ones? (either created by yourself or others)
I guess it depends on who is creating the scenario and how well tested it is. Scenario creation is not as easy as it sounds. It is easy to create something that looks good and then while playing you discover it is not balanced, not interesting, or just not fun. Hopefully, official scenarios have been play tested to ensure they are good; however, after a couple times playing the scenario, people will want something different. Custom scenarios can fill that space and they may not be tested as well as official ones.
How often do you talk in a game with your friends or strangers? (in person or online)
Often. Not much fun if you don't communicate.