In general, +2 to two ability scores is worth about a level.
Take a look at +2 con, +2 int. It gives more benifit than a basic level does. Better hp and skillpoints over time, increased fort save bonus, +1 to all int based skills. Thats the equivelant of a level and a few feats (or standard racial features) for the extra hp/skill points.
Now assuming that dex is as valuable as int, and most say it is, then +2 dex +2 con is as valuable as a level.
In the long term you get +1 defence, +19 hp, +1 fort amd reflex save, +1 to attack with ranged weapons, +1 to all dex based skills, +4 to ms and darkvision. Thats worth a level and a couple feats (or standard racial features) so it seems balanced to me at +1 LA.