xa_chan: - isn't the fact that every land unit automatically turns into a transport boat by entering a "water" hex a little strange ?
Not really... you need to research naval stuff to unlock the ability and they are completely defenseless, meaning you need to build escorts. You also need to unlock ocean travel and faster travel seperately... it works well and doesn't feel dumbed down.
xa_chan: - what about the fact you can't micro-manage much your city anymore (taxes, mood of your citizens, etc.) ? That there is no spy anymore?
Spy was added in an expansion before and probably will be again. As for city stuff you can manage it if you want to, but you don't have to.
xa_chan: - How do you feel about the fact there's no cultural and religious influence anymore and that the discoveries have been changed to tech discoveries and social doctrines, those last ones seeming not to have any real influence on your relations with other civilizations?
Culture is extremely important, it's like experience points in an RPG. You can largely ignore the social unlocks, but they are quite nifty to have and of course culture still expands your borders, all be it slower than in Civ4 so that you have to buy land. I like buying land, it makes sense from a growing empire point of view and it makes money more useful along with buying units outright, which is another great idea. In a war with too little units? Blow your treasury on a quick boost, but you might need that money later.
As for religion I do miss it sometimes and I hope it's put back in with an expansion, but changed significantly to go with Civ5's very different feel. I don't really know how to explain that... Civ5 feels very determined, very purposed. You must expand, either by conquest or by rapid migration, and you mist deal with all the city states and Civs. You can't steamroll other Civs anymore, if you want war you have to invest in tactical battles with fewer but more important units. Taking a city is a huge deal as they have great default defenses that are easy to buff up to massive strength. The game sort of streamlines a good number of things but then requires more investment and determination in other things, like war, expansion and picking which social trees to unlock. On prince or higher you really need to steadily manage your economy and happiness too, it's not like they hand it to you.
The game is not streamlined in the sense of making it easy, other than some AI issues they will likely patch. It's more streamlined on the back end because the front end is so much more tactical and needing of attention, if that makes sense. Less in the background, more in the foreground.