Well, flight is currently a better thing to have than a land speed. Whether or not this is a good thing, it is very obvious that every character will get an item that grants them a fly speed with good or better maneuverability, and possibly a higher speed than the 30 base that they have. This makes land speeds obsolete.
The problem that this brings up is the fact that there are so many things that boost land speed, and nothing boosts natural fly speeds, or flight in general (There is not a single official magic item that boosts natural fly speed. I checked. Everywhere. They're all land speed only.). Presumably this is because the designers wanted to balance things out, try and make flight a choice for maneuverability, and land a choice for speed. This failed however. Cause speed didn't matter as much as being able to fly.
As I was thinking about this discrepancy in balance, I was discussing possible fixes with Bauglir, and this is the result. Hopefully this will lead to a system where flight is not simultaneously over and underwhelmed by land speed. Though I have not added the boosts to flight yet, the system should be fairly straight forward, leading to fairly obvious feats/items. It uses the principles of larger creatures being faster, and faster creatures being less maneuverable.
By increasing or decreasing size, you can decrease or increase maneuverability, respectively. And by increasing or decreasing fly speed (but not just speed used in that round), you can do the same thing. The size categories are as follows: fine and diminutive; tiny; small and medium; large and huge; gargantuan and colossal, with medium/small defaulting at average. Every category larger reduces maneuverability by one step. For every category smaller maneuverability increases by one step. The bounds being perfect and clumsy, of course. This affects size changes, and also effects that grant flight, such as the *Fly spell.
Speed also affects maneuverability. The categories for speed are as follows: 0-25, 30-55, 60-85, 90-145, 150+. For every step slower you are, you increase maneuverability by one step. For every step faster, you decrease maneuverability. These changes are based on your size and maneuverability. For instance, if the Fly spell granted you a speed of 60 feet, and some effect slowed you down by 5-30 feet, you would increase maneuverability by one step.
With this, effects that increase speed for land only should be allowed to affect fly speed (natural only in some cases). There should be more effects that change maneuverability, and some that allow you to break the rules of maneuverability (like *Improved Flight, for instance).
*Changes to existing movement related spells/feats/items that I have right now for this rule set:
Fly (spell): The effect changes to a fly speed based on land speed. You gain a fly speed of 2x highest racial speed. The maneuverability is as your size.
Improved Flight (feat): Is not restricted to racial fly speeds.
Greater Fly (new spell): as Fly, but maneuverability increased by one step. 2 levels higher. Duration of 1 hour/level. Mass version is two higher than Mass Fly with the same restrictions.
Things like that would change. Of course, more will be to come, but I'm still not set on the speed half of the mechanics.