A few observations from someone who has believed in this game since Elemental was first announced:

First let me say that the polish and just general feel of the game has tremendously improved from Elemental.  I really think that Elemental suffered from being too ambitious and extra time and focus in the context of developing FE really shows.  Everything from the units to the sovereign/champions and the monsters just feels well-conceptualized and game really hangs well together.  We're not yet 100% of the way there (obviously since we're still in beta), but I honestly think that FE is light-years ahead of Elemental already.

Also, I recently took a break from playing FE non-stop to try out Warlock: Master of the Arcane.  Warlock definitely has its positives and negatives and I can't say for certain that I enjoy playing Warlock better than FE (or at least the FE as I imagine it will be at release), but I think that there a number of issues with FE where we can draw some lessons from Warlock:

1.  Capital protection: the first thing I noticed in my playthrough with Warlock was that taking an AI's capital was giant pain -- at least until mid-game.  Even once you had powered up units/siege units, you're talking about 5/10 turns of beating down defenses during which you're constantly taking damage.  In FE, I still get the "Faction x has been defeated" message in the first turn on occasion since some poor AI got placed too close to a lair.  Also, FE is still susceptible to an early rush strategy where a powered up sovereign can still wipe out a couple of AIs before they're able to get some traction.

Lesson: provide capitals with some real protection (something better than a free guardian statue) that prevents AIs from getting ganked by monsters in the first turn and makes it more difficult for players to completely wipe out an AI during the early game.  Perhaps a giant obelisk of doom would require the player to do some planning and engage in some "stategery" before taking down a capital city -- as opposed to ranking up a sovereign/champion as quickly as possible and just running through the AIs like butter.

2.  AI Aggressiveness: During my first playthrough of Warlock on normal difficulty, I was constantly under attack from one or more AIs.  Other than the early exploration turns, I think that there were maybe 5 turns where I was at peace with all factions and I didn't declare war a single time during the entire playthrough.  After constantly being the aggessor in FE, this was a welcome change.  I did feel like I was constantly being pressed -- often simultaneously and on different ends of my empire.  Further, although the Warlock AI is a bit inept on when on the attack, when it declares war, it does attack.  The FE AI will sometimes declare war and then do nothing for several turns.

Lesson: make the AI meaner and more crafty.  Increase the likelihood that an AI will declare war and make sure that it puts together some real resources beforehand so that it can act on that declaration.  Also, make sure that the AI is aware of the other wars that I'm fighting (I don't care if it is cheating), so if I'm off beating up an AI on one side of the map, the AI on the other side will try to take advantage.

3.  Monster lairs: Let me make one thing clear: the FE monster lairs, in terms of variety and difficulty, are far superior to that of Warlock -- except for the respawn feature.  In FE, once a lair is taken down, its gone forever.  In Warlock, you can be fighting wars on multiple fronts and suddenly an event occurs and there are all sorts of beasties are pounding on your unprotected internal cities.  I personally love that.  This feature increases difficulty and adds to the sense that the game board is alive and ever shifting.

Lesson: have certain lairs spawn during the game -- particularly once the game has reached mid-point.  Also, have the denizens of the lair really evolve during the game and rank-up significantly over time.  I once left a bear lair alone for a couple hundred turns and all it ever did was spawn a bear cub that did nothing.  If I leave a bear lair alone for a couple hundred turns, I would hope that a 3 headed giant bear comes storming out and tries to wreck my world with lasers shooting from its backside.

4.  Sovereign/Heroes Leveling/Unit distribution: In Warlock, I need all 4 heroes to be powering up together with several powerful units so that I can fight multiple wars on different fronts.  Even though I have had hero units with crazy offensive skills, my top unit (at best) is capable of holding off a single AI by itself until I can move other units over and counter-attack.  In FE, I start with a sovereign that, at least after a couple of levels, can hang with the lower level creeps.  After the Potential line of lvl-ups, knowledge and the +exp gear, the levels come quite quickly.  Eventually, with cloud walk, my sovereign is my only mobile unit, essentially steamrolling through the map.  The change to lvling did not have a significant impact -- I typically hit lvl 50+ with my sovereign.

Lesson: There is no magic bullet here to deal with the issue, but I think that most reasonable people can agree that a game where one unit can become immensely overpowered and essentially overpower every other unit in the game by itself (removing any need to build or level any other units) is not fun or terribly interesting.  Part of the issue is that the sovereign can attack and kill several different armies, teleport to other side of the map and then kill several more.  Another part of the problem is that AI keeps trying to zerg in a game where zerg doesn't work so well.  Yet another issue is that the game's set up envisions an environment where 100+ hp, 30+ attack and 30+ def is top tier unit when that's just not the case (my sovereign typically ends up with 320+ hp, 100+ off and 100+ def).  Perhaps a mechanic where units are limited in attacks (or at least require a skill to attack more than once per turn), reducing movement points to zero for the rest of a turn after a teleport, tweaking AI unit development and strategy and/or providing for monsters that respawn/rank-up to at least run somewhat in parallel with sovereign/champion development would be helpful.

Anyways just a few observations.  I'm not asking for a carbon copy of Warlock (which I think is a generally inferior concept), but it occurred to me that there are several lessons to draw from it to improve FE.  Fire away.