I've been examining the Thematic Theme Framework for WordPress (http://wordpress.org/extend/themes/thematic). I just got a job at a shop that does a fair amount of WP hacks and I'm examining Thematic for use as part of our 'standard procedures'. I have themed WP a few times, just by copying twentyten or twentyeleven and then modifying it, but I'm at a point where I need to get deeper into WP to start overriding and really extending it (my PHP skills are decent). My question is: in your opinion, is Thematic worth using? My concerns are:

* performance hits on shared hosting where PHP is being run as a CGI binary and performance may already be not-so-hot
* what is the point of hooking into Thematic's functions (that hook into WordPress) instead of just hooking directly into WordPress?
* if the Thematic project is abandoned because the developers all die in a plane crash a la Lynyrd Skynyrd (or for other reasons) where does that leave me?

I'm just having trouble seeing the advantages to using Thematic - what does it offer that WordPress doesn't do already? I'm looking for a justification for learning development with Thematic instead of just learning WordPress development directly.

All your rants are appreciated :)