I'm pretty sure that the income bonus being given to all civilizations, not just the player's civilization, is exactly what he intends.

Personally though I think giving a tax revenue bonus alone wouldn't speed up development so long as we're stuck at 100% production capacity maximum. You'd have a lot of extra money but research and building wouldn't be faster unless you purchased things to speed it up, so this would require a change in strategy. More research buildings, less industry buildings, and probably a greater emphasis on population and income. I'm not sure if the AI would be able to adjust without modification.

Increasing industry capacity effect by whatever amount the income is being increased, would cause this idea to make more sense to me. Would it increase the advantage that economy-maxing civs get? Yes, but pretty much proportionate to how much advantage they already get, because civs that emphasize research, industry, pretty much anything would be given a boost either directly or indirectly, too.

I'd also like to point out-- well I've only played two games so far in 1.3, so I might not have noticed everything-- but things don't seem too slow so far. I just don't notice the difference in speed from how it was before.

It's already possible to select AI bonuses through their intelligence level. The AI gets bigger bonuses on economy and production at higher levels.

It think the OP is implying the game should provide the same type of thing for the human player. Actually, you can already do that (in effect) by tweaking your racconfig file. Though, it doesn't work for Metaverse games since non-stock raceconfigs are disallowed.