Experience Table
An area of major improvement from 2nd edition to 3rd edition was the experience table. Before 3rd edition, the table varied from class to class and while it had a pattern, it was not easily describable. Players had to guess and assume that the differences between the charts and each level were designed correctly and fairly.
In 3rd edition, the chart was simple and unified. Every class used the same chart. The amount of experience needed from one level to the next was equal to 1,000 times your current level. Beautiful and simple.
In 4th edition, they have retained the concept of one chart for all classes. However, the nice progression table that once govern the experience is gone. The table now has some patterns, but no one pattern that continues through the entire table. This change is simply annoying. A problem that had been solved has returned. They could have done everything else the same in 4th but found a way to keep a simple table for experience.
Like many of the changes, this one will not alone prohibit anyone from changing. But it is another knock against the system. Another change that wasn't needed.