I wonder whether a similar, but more granular, experience could be had (I'm looking for the same thing) by dividing the XP awarded by monsters and other encounters on average in half. It would do the same thing as doubling the table, but it means that you could stretch out or shrink particular sections of the table by changing the percentage used: making the early levels longer by dividing XP awards more (25% normal?) or bringing upper level advancement closer to RAW (75% normal?), for example. I figure that altering the award-side versus advancement-side also makes it less complicated for the group as a whole since the players don't need to do any different math or use different tables, just agree that they'll advance slower than expected (and the DM just needs to multiple the XP total by a percentage before awarding it).