The con bonus is of the enhancement type and therefore, at only a +2, is of extremely limited use as that is the very minimum even an endurance spell would give you (not to mention any magic items of the enhancement type). It is useful at low levels, but with the extra turning prereq, it would be rare that anyone besides a cleric would use the feat - whom specifically get endurance as a spell at 3rd level (and if nonhuman would only gain access to the feat at 3rd level). Therefore, the feat would probably be more useful for a paladin. However, Paladins don't get turning until 3rd level so could not take extra turning until then, meaning to get the con bonus they would have to take the feat only as early as sixth level. At sixth level it should be pretty easy to have access to an endurance spell.
Now, in a magic light campaign, where the endurance spell or respective magical equipment is extremely hard to comeby, the con bonus warrants more serious consideration - but it is virtually useless otherwise. If they errated it to be an unnamed bonus, now we're talking. This is what I have done in my game as a houserule.
The speed bonus is a whole other ball game. The speed bonuses would stack with other increases in speed (like fast movement from a barbarian and the expiditous retreat). Moreover, getting the feat at 3rd or 6th level (with the respective cleric and paladin) is very useful as at those levels, an increase to (probably) 30 or 20 feet for medium size/small size creatures respectively is tremendous.
What is even more useful however is for characters who get the turn undead ability but have very limited use of it due to not having all their classes contribute to it. Thus a Cleric shooting for to be a fleet runner of Elhonna for example could make great use of the speed increase. Another good example is a Paladin/ Sorcerer. An unarmored paladin sorcerer suddenly with a speed of 80' is quite a powerful foe because he can move away to the limits of his medium range spells and be too far for most short range (be it SA, melee, or short range spells) characters to reach in one round - rinse and repeat. Really, for any character that can capitalize on movement - be it ranged abilities, hit and run tactics (be it spring attack or otherwise) the speed increase is nice. The catch is being as useful as a different feat in its place. The con bonus as is does not push the feat over the threshold as useful enough as by comparison enlarge spell, far shot, or spring attack for the respective types that would use this feat. However, changing the con bonus to unnamed does make it worthwhile.
I voted of limited use as is, however, if you houserule the con bonus to unnamed I would then say the feat increases to a 5 or 6.