I'll answer the basic questions for you. Obviosuly I like it, hopefully others will give their views.
1) How is basing achieved? I saw from Than's Games' website that the miniatures are individually based. In 15mm I'm guessing on 1/2" squares, then on movement trays.
As long as your opponent uses the same system (or you able to mentally accomodate differing base sizes), there are no issues. However, I generally suggest a 15mm base for a 15mm figure, and a 25mm base for a 25/28/32/whatever figure. There are 5 base sizes that the game addresses, and all are multiples of that single base standard: Base 1 (standard infantry), base 2(standard cavalry), base 4 (standard bigger than man: ogre, troll, bear rider, etc), base 9 (Any huge mnster or vehicle - giant, dragon, etc). There is also a base 1/2, which is for halflings, sprites, etc.
So if you are using base 1 = 1"x1" base(or 1" diameter circle), then base 4 is is 2"x2", base 9 is 3" X 3", and base 1/2, is either 5/8" or 3/4".
I have steel bases for 15mm and 25mm scales, but you can also just get washers. Or mount them in larger blocks to cardboard or magnet and use casualty caps.
2) How well (or poorly) are the force design rules presented? Are the stock army lists pretty complete?
I won't answer the how well, others can say. If you look on the website in the AoA support section, look at teh "3rd to 4th changes" section, and you can find all of the force lists in the book. They are laid out in a no frills way.
The stock armies cover about 90% of the WHFB line for similar armies, though these typicaly have a few more options to make them into what I think of as sensible. Those units that aren't in the book can be addressed with the point system. I've been told that people can find a Demonworld 15mm figure for most of the stat lines in comparible armies, as well.
3) Is there an excel sheet or similar mechanic available to aid in unit/force design?
A guy did create a perl one for making new stat lines on the web, and several people have made excel ones. I don't think any of them cover all possibilities perfectly, but it is very easy to do by hand.
I think there are AB files, but AB does not cope well with the AOA stat line, so I find its usefulness limited. You can cost out your armies, but I don't think the sheets come out coherently enought to be be used as references during battle. Most troops are very easy to remember stats for, so there is very little referencing needed during the game anyway.
Otherwise, the only limitation on building a force is the 60/40 rule - at least 60% of the points have to come from regular, non elite troops (and non elite monsters if you want to play very high fantasy), and 40% can come from elite units, monsters, characters and artillery.
And you can violate that rule if you really want to and you opponent doesn't mind.
4) How does it play?
I think in the AoA description on teh website it has a good breakdown. But in general...
Turn sequence is: Move Fleeing units, initative, one player moves, second player moves, players alternate casting with their mages, missile fire is resolved simultaneously, melee is resolved simulataneously (excpet for first and last strike), morale. If you've played warhammer, this is the exact opposite feel, as you don't get to pound on your opponent with little fear of suffering casualties back.
Magic works by each mage focusing a point of power per turn, then alternating casting actions. A level 1 spell cost 1 point, a level 3 spell costs 3, so to get the big spells out, you need to save up a few turns. Power can also be used to counter an opponents casting. All spells require LOS.
Missile and melee are very simple. A figure has X attacks at Y skill. Roll X dice for each attacker, needing Y or less to hit. To hit is modified by a very few things, and some models have evasion to be harder to hit by 1 or 2, and some are slow to be easier to hit. If you hit, the opponent gets an armor save, needing to roll his armor value or less to avoid the wound. Strength from the attack reduces the armor value, so when saving a hit of strength 1 on an armor 3 creature, you need a 2. Some armor is fixed, and is not reduced by strength unless the strength is magical. Some weapons attack the magic resistance of a creature instead of armor.
All missile fire is considered simultaneous. All melee is considered simultaneous, except for first strike (from ramming, long weapons on the first turn of combat, or just being fast).
Morale comes after all combat is resolved. This means everything gets to fight before running away (except 1 spell effect). It is 2d6 based. You have to have something significantly detrimental happen to a unit before it has to test - significant casualties, losing a leader, or being in combat with a superior unit. Casualties affect the roll, as does the mass of the units engaged - being in rank and file gives good bonuses to morale while being in skimish makes it more likely you will have to test and more likely to fail the test.
5) How quickly can someone pick up the rules? Is it suitbale for convention play?
Very easy to learn, most people have the basic principles down in one turn. There is a LOT of flexibility in strategy, and that keeps the game fresh a long time. It is very suitable for conventions, both for scenario or bring and battle events. The rules adapt easily to a lot of scenarios - we play free-for-all games with as many as 6 people, we've played games only using a few monsters attacking a village (to see who could eat more peasants, lol), we've played small skirmish games with 20 figures a side, we've played huge games with 600 figures per side. An average game is probably 80-200 per side.
may be slow, but... well, he's just slow.
