All right...so I actually took time to download and play this map. I usually like freebuilds because it's just a wonderful sandbox to play around in and have fun with. This map was no exception. I played it...then replayed it, then replayed it, then replayed it, then (do you detect a pattern?)...anyway, it was excellently enjoyable. On to the review!
Playability obviously takes high marks. The one thing detracting from a perfect score, at least for me, was the pre-built castle. In a freebuild, it's usually a start-from-the-ground-up setup which allows the player to experiment. You kind of cut that down a bit by having only one spot a castle could be built and by pre-building the castle structure. While it DOES look nice, it kind of detracts from the complete openness that is the hallmark of most freebuilds.
Balance is average. There weren't too many natural challenges except for the odd wolf and bear attack. I also tested my castle against several invasions of varying strength. Each time, the castle held firm with few losses. Ordinarily, this would garner a low score, but a freebuild is generally not a combat map, so balance cannot be judged on that alone. In terms of overall setup, it was good. There was a good amount of space for building that neither limited it nor allowed too much of it. It was rather easy to get a good, efficient economy going, and just to sit back and enjoy watching your settlement expand and grow. So it averages out.
Creativity also ranks at average. Again, while this map is really nice in a lot of aspects, it is, no insult intended, nothing really new. Things like submerged granaries or lowered walls have been done and done, and while the limited options in this map do challenge the player slightly to rely on methods that they possibly usually don't, it's not enough to distinguish itself too much from other maps of its type and style.
Map Design takes high marks. It was excellently done and deserving of a high score. It's not the best that has been seen, but it is definitely one of the better ones. It flows well together and is nice to just look at. It also factors in strategically on the marshy lowland in terms of farm production. It was well done by all accounts.
The Story/Instructions score takes perfect marks. As you said in the web page description, you loaded it down with a lot of information, and that was no lie. There is enough background information on the Anglo-Saxons provided to write a short research paper.
Overall...you've definitely made an excellent start for yourself on this site, and in my opinion it's a worthy addition to the ranks of Stronghold Heaven maps. All technical points aside, it was just simply a LOT of fun to play through. I eagerly look forward to your next work. Again, well done...and keep designing!