I have flown Jet a number of times in the last twelve months and they are very good - no complaints at all and in particular the cabin service is excellent.
I was normally flying Jet domestic in and out of Mumbai on slightly older 737 metal - my only complaints were horrendous ATC delays into Mumbai for domestic, though it never seemed particularly bad for international flights.
As others have said, its the roads of Mumbai or Bangkok that will get you before Jet Airways will!