Of course, they do! Although I haven't playing much about PlantSims, this is what I can tell you:
Special abilities:
1. You can access Photosynthesize interaction. This will recover Energy and Water needs for that PlantSims.
2. You gain two type of kiss as special interactions.
- Flower kiss: this will give the target an 'Obsessed' moodlet for 8 hour and this interaction is considered as flirty.
- Poison kiss: I notice that I can unlocked it when I have a sims as an enemy. For the plantsims itself will gain 'Hydrated' moodlet that can boost their mood +30. For the victim they will have 'Poisoned' moodlet that last for 3 hours and suffer their mood for -25.
3. They can 'Commune with Plant'. The option that you can get:
- Ask About Day
- Get To Know
- Compliment
- Imply Mother Was Acorn
- Flirt
And it's seems the plant is talking back too to them. It's kinda creeped me out (look at plant not plantsims).
I don't know about what effect that can give them. Maybe somebody could point this out?
4. When they are walking around there's seem to have a special effect, like a trail of flowers.
5. I don't know if this can be called a special abilities, but others say when PlantSims try a baby they produces seed.
Skills: Don't know yet, so I can't say much.
Needs: Their Hunger and Bladder don't decay. The new one is Water.