Unfortunately power is still a problem. While there is part of the standard for power, Apple went the other way so high power chargers have to support Apple or open standards but not both. Todays tablets have very high capacity batteries (and they keep getting bigger) so various manufacturers have been going proprietary again in order to increase power from the charger (Samsung Galaxy Tab 10.1 is an example).

Here is a post showing someone trying to get a standards following USB charger:

https://plus.google.com/117091380454742934025/posts/5suTrJrp...