I started with TP 5.5...
At some moment Borland released, free as in beer, the 3 and 5 versions. Binaries should be out there somewhere for those curious.
I'm sure young people would be surprised to see what 5.5 provided. The on-screen help was amazing: cut and paste useful examples from the help of many functions. And the instantaneous compiling... :)
I started with 4.0, so that's my baseline. Then 5.0 added overlays (IIRC) and 6.0 introduced Turbo Vision, which was a kind of magic to me :).
It's interesting how a _programming language/IDE_ can bring such warm feelings.
Do you remember if there was any major language feature added in 5.0? I couldn't quickly find anything concrete..