Personally I'm not a fan of the 'Age of' titles, my brother has them and loves them to bits but they just feel boring and fiddly to me. Like they're trying to be an RTS and a Civilisation-Clone, and felt like they missed the point of both.
Graphics don't make the game, but it'll make it sell so s'pose it's a good thing they've finally decided to embrace the 3D age with a giant leap. This said, Pixel Shader 2.0 or 3.0 makes no odds visuals wise; the only thing that Shader 3.0 adds is the ability to make environments feel more alive and run quicker, graphically anything you can do in 3.0 can be done in 2.0 as well.
Best example is probably FarCry, which from screenshots looks identical but when you see the video of the different versions and watch the tree's sway and such. Really adds to the overall feel of the game.
It'll be using Shader 2.0, and no doubt 1.1/1.4 to capture the largest market... while not looking *as* good as it does there, it'll still look pretty damn nice. Anyone seen Settlers V? Uses the dated Warcraft3 Engine but with Shaders. Looks bloody gorgeous to play without killing computers it runs on, especially considering the density of people and building you have in-game.
Same goes for games like Battle for Middle Earth, while the Shaders help the games look amazing, polycounts for the moment are remaining quite low which allows alot of cards to handle them from the low-end to the high-end. As developers generally put in a blend to use one or the other and not rely on one too much.
Well there are exceptions, ::coughD3/HL2cough:: but generally speaking you see a blend being used to produce a much higher quality image without much effort.
For example, Prince of Persia : Warrior Within uses just a simple Shader 1.1 Bloom & Field of Depth, with just bog-standard graphics style from 2000-ish which works a treat and makes it really seem modern.
The same effects that are very easily recreated in DarkBASIC Professional and appear to be being used in AoE3.
It's the easiest way to improve graphics cheaply. From most of those shots you an quite clearly see that it is using alot of effects that would be easily recreatable in DarkBASIC Professional with not alot of effort. Shadows would slow it down given how DBP does them, but generally I'd say that you could get that running most of those screenshots with a half-decent engine @ 1024x768, on say a 2.0GHz w/256MB w/Shader 1.1 64MB Card very easily within DBP... within a professional engine that is optimised could probably go as low as 1.2GHz 128MB, maybe even use a Fixed-Function card like GeForce4 Mx