In the Steam version, there are 8 achievements that can be unlocked:
- Executive Producer of Goo Product
- All Levels Complete
- Subversive Traveler
- there is a secret (spoiler)
- Engineer of Goo I
- All OCD Flags in Chapter 1
- Engineer of Goo II
- All OCD Flags in Chapter 2
- Engineer of Goo III
- All OCD Flags in Chapter 3
- Engineer of Goo IV
- All OCD Flags in Chapter 4
- Engineer of Goo V
- All OCD Flags in Chapter 5
- The Architect of Goo
- All OCD Flags
Completing these achievements gives you nothing except bragging rights on the Steam website 
.