I was part of the King Arthur: The Saxons beta team in the last couple of weeks, and I must tell you that the Saxon expansion is a great sandbox expansion to King Arthur - The Role-playing Wargame from Neocore.

After playing quite a lot as a tester, here are my impressions about King Arthur The Saxons:

Battles:
There are numerous new units in this expansion, you can also hire some special units, like mounted archers or even the protectors of the one and true Faith: the Guardians. They are just awesome. Here you can still go to battle in a lot of different ways: Will you go bluntly for the enemy, have your whole army charge, and pray for success? Or will you take the time to use all the great tactical possibilities of the battles? Outfit your hero properly in order to specialize him, and make him a great units commander, an unstoppable warrior, or a heavy repeating spell caster. Use the various terrain types, formations, stances, unit types, and so on for some decisive tactical advantage. Battles are always so exciting, but the very best is yet to come ^^

The campaign. The best part ^^.
So, here I am, knee deep into the sand. So, what to do next? There are a few quests to follow, but those are just guidelines. So, talk to that king, offer him gifts, and then take him as a vassal, date a bride to be, and ultimately make her your queen, try to recruit some powerful heroes, befriend the Sidhe, the outlaws, not even talking about some quests to recruit even more heroes, gain powerful artifacts to wage war with, or help you rule your kingdom wisely. Will you go for a defensive stance, buying kingdoms around you, and obtaining their vassalage, non aggression pacts, or whatever? Or will you plot in their backs, sending them to war against each other, recruiting powerful mercenaries, and preying on the feeble whose water you just poisoned... The sheer amount of possibilities on the campaign map is overwhelming, and you will have to think and make some hard choices if you want to make things "right". And this amount of choices, alliances, and deeds to freely perform is what I really love about the game.

And of course, all this on the beautiful map and in the beautiful music of KA.

Ok, so enough writing for me, some ruling awaits...

"SAXONS, stand firm behind your king, for the time has come to spread the Faith of the Lord. TO WAAAAR"

It is already available through Steam.

Don't forget to mention about Diplomacy system.

well I just bought this, have been playing Crusades. love that game. I will let ye know about this Saxon, after I play it a few times.

I would add my two cents from my yet-unfinished campaing as Raedwald:
1. Saxons is effectively what you have in King Arthur once you get your stronghold and don't follow the storyline to closely but rather upgrade, go to a little war here and there, do some side quests.
2. The diplomacy system is decent, however, the special diplomatic events (e.g. marauder attacks or spy attacks) make sure you don't expand too recklessly in the very beginning.
3. it is HARD to get all that necessary ruler christianity going. in KA vanilla i was able to move christian-wise simply by enabling canonical law (it would give +1 per year), here it gives you only 1 (in total) move towards christianity. i.e. you need to do quests right, otherwise you're stuck with breakshields!
4. there are now text quests, which is lame, however, you get interesting artefacts to collect and knights to recruit.
5. as a cavalry (i.e. trampling) based army you will find it more difficult to level knights and units up (they don't fight the enemy and don't get xp, they make mincemeat out of the enemy running them over... apparently, poor educational value in that)
6. prepare to have a LOT OF CASH. i played KA vanilla in HARD and cash was not too scarce, but scarce enough. here, i am a pig with over 200 000 food and gold, HARD as well.

7. I got the guardian units and the "arch guardian" spell, so I am throuncing everyone. cash is getting scarce, however, as I went into a recruiting spree (who wouldn't like to have an all guardian/sangreal knigh army). those bastards cost a lot
8. it seems I am comming to the end of campaign. I don't own 8 provinces, and no one can hope to challenge my armies.
9. do pay attention to "leadership" requirements for more heroes in an army. 3 heroes is enough and I am having it relatively easy now.
10. do collect artifact sets even if it involves losing 3/4 of your most powerful army. artifact sets are op!!!