Forgive me for suddenly weighing in on this, I only just read this thread!
It seems to me that the concerns over combat realism arise out of the fact that Civ games are designed with the maps and turns retaining both a strategic and a tactical context at the same time. In the strategic context (city development) a forest tile represents miles of dense forest, river tiles are able to represent networks of river and natural irrigation, and hill tiles are capable of whole areas of hilly terrain. In this context a turn passing represents a strategic amount of time passing, as the game date shows.
In the tactical context (combat), the mechanics are set up on a much smaller scale as resembles Battle for Wesnoth. A forest is merely a collection of trees large enough to conceal an army and provide defence, a river tile represents a single river that can be fortified behind and a hill tile is a single piece of high ground that could be exploited by soldiers and archers and the like. The passing of a turn in this context represents a far shorter amount of time, perhaps even just 5 minutes within a battle for specific combat tactics to be executed.
This retention of both the contexts simultaneously is what makes Civ so accessible. By representing both the tactical and the strategic in a single set of graphics on screen you can keep the presentation very clean and uncluttered and most importantly it enables the player to understand both the strategic and tactical situation by merely casting an eye over the map.
The tactical combat mechanics - using relatively small amounts of units to execute entire wars is merely an abstraction as has been already mentioned. It's not the same as the detailed simulation of war that features in other games, but it's part of the magic recipe of Civ that helps them to streamline the gameplay. I don't think that will change, it's as much a defining feature of Civ as the real time tactical combat resolution of the Empire Series. At least those who want to make a realism mod to move towards a singular strategic representation of both civ development and war, will be able to do so and distribute it easily and build a community round it more easily in Civ 5.
As regards the new 1upT mechanic specifically, I think it's very promising. It means that throwing large armies against someone won't require sifting through stacks to predict how attacking will pan out, as all the units will be laid out over the terrain and the situation can be scrutinised and understood by eye. It's more of the same accessibility that Civ is known for and other games have shown that that style of combat can be great fun.