I reflected on the importance in Polish of distinguishing between wyjazd ˈvɨjast and the very similar wjazd vjast, ‘entrance’: one letter difference, one phonetic segment difference, but just the opposite meaning.
Rather more common in public signage, it seems to me, is another pair, equally confusing: wejście ˈvejɕtɕe ‘entrance’ and wyjście ˈvɨjɕtɕe ‘exit’. Many buses have two doors, one marked wejście and the other marked wyjście. These two words differ by just one letter in seven, just one phonetic segment in seven (or six, if you count an affricate as only one segment). Native speakers, of course, take in their stride what looks to outsiders like a stupid design flaw in the language.
It does mean, however, that any speaker of Polish has got to be fully sensitive to the difference between e and ɨ. That includes NNSs trying to get their tongues around the language (blog, 7 July 2010: note that on that occasion the hamfisted respelling supplied to us for omijajcie góry, lasy, doły was ‘o-me-yaiy-che goo-reh laseh doeweh’, ignoring just this contrast).
What is even more interesting in this connection is something I have noticed about Polish /e/. This vowel is often transcribed more narrowly as ɛ, but I am wondering if an even narrower symbol ɛ̈ might be appropriate. It strikes me as often being considerably centralized. I’ve noticed this particularly in the final vowel of the placename Katowice, which tends to sound closer to English ə than to English e or eɪ. I got a helpful informant to pronounce jeszcze dziesięć ‘ten more’ — yes, ˈjɛ̈ʂtʂɛ̈ ˈdʑɛ̈ɕɛ̈ɲtɕ.
However, Jassem’s Polish vowel chart (reproduced here from Wikipedia) shows the vowel as fully peripheral. The Wikipedia article makes no mention of possible centralization. Likewise Biedrzycki, in his Abriß der polnischen Phonetik (1974), plots this vowel as coinciding with cardinal 3 and comments merely (p. 60)
Das polnische Phoneme /ɛ/ wird hauptsächlich durch den vorderen halboffenen ungerundeten Vokal [ɛ] repräsentiert… Dieser Laut erinnert an das deutsche kurze [ɛ] in /bɛt/ Bett. The Polish /ɛ/ phoneme is mainly realized as the front half-open unrounded vowel [ɛ]… this vowel is reminiscent of the German short [ɛ] in Bett.
This centralization, if I am right about it, must make the wyjście — wejście distinction even harder to hear.