I think that there's a lot of negativity about the Forest Spirit nerfs, but I actually think Treekin and Treemen do well out of it as they get significant points decreases. Sure they lost a pip of strength, but evidently the designer doesn't want these models to be winning many combats, and rather tanking something. The one exception is the Dryad nerf which I just cannot get my head around. Drop them down to 9 points per model and they are much more reasonable.
Still, its very fair to say that the army lacks high combat strength, capping out as it does at 5, but I think that's a completely reasonable (and fairly interesting) gameplay choice given that they have so much anti-armour at range. Having both would be a little too far, imo.
The mobility is all still there: just take the no modifiers arrow upgrade and move and shoot to your hearts' content - without having to worry about any other penalties, too! Or take the poison upgrade and play the Skink game. Losing S4 at short range is a blow, but again - can anyone say that they think that would have been reasonable to keep this when combined with poison shots, no modifier shots, flaming +1 to wound shots, or AP-3? Making it an arrow upgrade is also a bit too good when those bows are already Armour Piercing. S3 AP with the available upgrades seems very reasonable (My Dark Elf Crossbowmen would love Poison upgrades...).
The only Skirmish option lost is Dryads btw - all the others are still there, and with Scouting AP arrow upgrade Skirmishers in Special, ASF Wardancers, and the huge buffs to Wildriders and Waywatchers, arguably got better.