IMO the more house-ruled a particular campaign is the more important it is to be up-front about the house-rules. I try to be methodical and generally try to keep to the rules as written as that way its easier to get and keep players.
If I had a heavily house-ruled game I would write out the changes on a sheet, and when recruiting players would given them the sheet so they knew what the campaign entailed and didn't have misconceptions when they actually sat down to play.
It's much better to find out that someone won't like the game quickly, rather than fit a square peg in a round hole.
As for the 4e rules, in general they look good to me. There will be a lot less magic items found in the average 4e campaign everyway - monsters won't need a load of magical crap to challenge the party that will only be sold as loot. The magic items that are found will be more significant (they should be picked anyway, but their greater rarity will make them stand out more).
As for the buying and selling of items, this is one of the most heavily house-ruled areas and I see this continuing. There are a lot of strong opinions on the topic. See above
Re the identifying question, I prefer the easy option. I have seen it being made ridiculously difficult to ID magic items, something that is very off-putting to new players.
Remember, unlike previous editions, all the power sources can be at least a little magical.