30 feet in 6 seconds is 300 feet in a minute is 18000 feet in an hour. That works out to 3.4 and a bit miles an hour. That's pretty much normal walking pace, and not a jog at all.
It puts a jog (hustle or double-move) at 6.8 mph, and a full run at 13.6 mph.
Check out pg. 163 of the 3.5 PHB. You are partially correct, but didn't read it all.
Hustle: A hustle is a jog at about six miles per hour for an unencumbered human. A character tha tmoves his speed twice in a single round....
That's the part you addressed above. But, there's more.
....or moves that speed in the same round he performs a standard action or another move action is hustling when he moves.
Now maybe I've read this wrong, and if I have correct me, what what I see is this:
Perform 1 Move action in a round and nothing else, you're Walking.
Perform 2 Move actions, or perform 1 Move action and 1 Standard action during a round, you're Hustling.
Therefore, half Speed is walking speed.
Now, I'm more than willing to be corrected. And, I would like someone to correct me if I've read this wrong. But, that's what it looks like it says, to me.
EDIT: I'm going to leave the above even though I've found evidence that I'm wrong. It explains where I was coming from.
If you look at the Movement and Distance Chart, regardless of how the rule is written above, it shows a Walk = 1 Move Action. So, Greenfield is correct, and what I said is off the mark.
The chart shows Walk = 1 Move Action and Hustle = 2 Move Actions (which is wierd, given the way the rule is written above--though the chart makes more sense).
2nd EDIT: This is interesting, too. I'm looking at the RC, pg. 92. This might shed some light on the screwy language in the Hide + Movement rule.
It says:
Move between Cover: If you're already hiding thanks to cover or concealment, and you have at least 5 ranks in Hide, you can make a Hide check (with a penalty) to try to move across an area that doesn't offer cover or concealment without revealing yourself. For every 5 ranks in Hide you possess, you can move up to 5 feet between one hiding place and another. For every 5 feet of open space you must cross between hiding places, you take a -5 penalty on your Hide check. Movement speed penalizes the check as normal.
First off, this looks like a totally different rule from the one included under the Hide skill that we were using above. It doesn't mention getting the distance of 1/2 Move without penalty.
But, if you do get the 1/2 Move without penalty, and you have Speed 30, then (and you assumed the penalty maxed out at -20)....
5'-15' (1-3 squares) no penalty.
20' = -5 penalty.
25' = -10 penalty.
30' = -15 penalty.
35'+ = -20 penalty.
Either way, that's a different rule from the first one we saw....maybe a change in the editions, from 3E to 3.5E?