vb.net isn't VB. That's about all there is to it. If you're going to learn a new language, why learn VB.net when you could learn C++.net and be able to do the same things and more?
VB6 is very similar to VBA, which is used for MSOffice scripting, so probably worth knowing.

My first language was Advanced Basic (BASICA.COM, came with DOS 3.3). Learned by RTFM.
My second language was Turbo Pascal 5.5 (with OOP). Learned by RTFM.
My third language was Turbo Assembler. Learned by RTFM.
My fourth language was C++. Learned in HS. Cheated a lot with inline-assembly at first...
Past that I've learned anything else by the method previously stated.
Eventually learned OWL and MFC in HS, wrote windows apps when my peers were writing console apps for assignments.
I skirted with ASM for a while, but never really learned it
Learned C (or rather the differences between C and C++) for my job.
Eventually learned PHP to work on this site.
Eventually learned javascript to write the chatbox (had skirted with it before, but never really understood what I was doing)

This is excluding minor languages like WordPerfect macroing language, calculator programming languages, etc. There are also non-procedural languages that I've learned like HTML, SQL, XSLT, XPATH...