AoE3 - Revised offers a less restrictive Age of Empires 3 experience and aims to make the game more like it's predecessor.
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I'll comment on the two features that I like the most:
1. The category-based population slots for all units (i.e. 1 slot for infantry, 2 for cavalry, and so on)
It's great because back in Age of Empires II my Teutonic Knights or Paladins didn't take an extra slot because they were more powerful than regular units. Being elite units, they were expensive, and as such they were limited/regulated by your own economy. If my army is composed of highly trained soldiers that cost me a King's ransom, why do I have to train them in even fewer numbers because of an unreasonable rule? If you ask me, even the cavalry should get 1 population slot because they are countered by so many cheaper units that you can't compare them to the almost god-like AoE II paladin.
2. The removal of building restrictions, the increased durability of all structures and the possibility to build up factories and forts on your own
There's no need to explain the reason why I like this feature. Every turtle-nut coming from other RTS's was disappointed to see there was no buildable fort/castle-like structure, that towers/outposts were restricted to a limited number, that cheap artillery and infantry could throw an endless stream of cannon balls and molotov's at your bases and raze everything within seconds. Whilst to some extent I believe the importance of defensive buildings progressively decreased through the centuries - beginning from the early modern era - I also realise that what makes playing on the defensive so pointless is the rate of fire of artillery units. (e.g. Indeed a western cannon could take down simple outposts in a handful of firings, but rearming the weapon took ages and not less than 10 seconds). In Age of Empires II siege weapons were generally slower, and not as effective as the ones in AoE III - the only exception being the trebuchet, highly renowned for its slow speed and packing/unpacking time. You could say the bombard was also really effective, but not all civilisations had that, it was available late in the game, was expensive and could be dispatched with a couple of crossbowmen.
As for the possibility to build factories, it means to have an economy that is actually on an industrial scale/level, which is damn good as well as realistic. I love buildings that produce resources on their own - too much microing in the late game when massive battles occur is really annoying. AoE II was sort of lacking in this sense, because no resource renewed itself without microing at least a bit (farms still needed to be queued at the Mill).
Looking foward to it! :)....... ............. ............ ........... ..................... ............ ............................. .............. . ........... ........ .. . .. ........ .. .... ................ (i had to complete 150 characters)