Good playability - played against two Fredericks with a Lionheart. I had to produce stone to generate enough money to run the rest of my economy, adding some difficulty. Fun to play!
Balance wasn't bad at all. However, the resources could have been spread out a little more, and less cramped; I had some difficulty building my castle around all of the trees beside my keep. O_o
I've seen a lot of maps like this - river in the middle, and players in the corners. However, you didn't do too badly here; good for a first map.
Map Design: 2.5
Now, I'm not going fire a tirade of criticism at you, as its just your first map. However, I am going to make some suggestions. The biggest one is to simply get to know the editor really well. Know all the tools available to you, and the fact that although the Crusader editor can't make sweeping landscapes like the original editor, it specializes in something else - making barren, desert landscapes. Also, whenever making a map, always ask yourself, does this look real? Does it look natural? For example, there were two little ridges around the center. Why are they there? They just sort of popped out of the ground. There wasn't much of a gradient there. Also, the iron - try to place it near a rocky outcrop or so, as it looks better and more attractive, meaning more downloads. Try to stay away from the resources in the corner thing people tend to do. Why is there oasis grass in the corners? There aren't any water sources, but there is just scrub by the river. Always make things look natural, and you'll get more downloads, comments, and reviews.
Contrary to popular belief, skirmishes should have stories. Just take a minute or two and think up of a short plotline or hook. As for instructions, they weren't bad, giving the player tips on rushing and such.
Additional Comments: Biggest suggestion - spend time with the editor, get to know it, and spend lots of time on your maps. This results in a polished, refined, natural look that'll be sure to get lots of downloads and reviews. Always try to make your maps look natural.
However, don't get me wrong - this is a good first map! This is a jumping off point for any further maps, and I'm looking forward to seeing your next map!
Welcome to Stronghold Heaven, and I hope you'll be a great active member here. Well Done!