As always the best answer comes from Ubuntu forums where a dude mentioned that certain tweaks need to be done to the samba server configuration. Namely, password encryption has to be enabled (even for 'share' level of security)
encrypt passwords = trueApparently, Apple doesn't give a shit about its users (as usual, I suspect) to ever mention the little fact that OSX SMB client can't work with SMB server where password encryption isn't enabled. No help, no web information, no nothing... While producing a pretty good yet overpriced hardware for their laptops there's still much to do to make the software better. Having cool iPhone features added to the PC OS doesn't make it any better, I guess.