Laughs in Polish
But honestly, I think both have pretty similar difficulties:
Voiced vs. unvoiced consonants (morphological spelling) - same here.
Pairs of letters representing the same sound (historical spelling) - same here.
Not always following the "write how you speak" rule (like words beginning with "j + consonant" or clusters like in "zvláštní") - same here, especially words whose direct pronunciation would be considered hypercorrecting: "sześćdziesiąt" (pron. "sześdziesiąt"), "dziewięćdziesiąt" (pron. "dziewiędziesiąt").
The only stuff we don't have is long vowels vs. short vowels, and here I'm curious - do Czech people consider some of them difficult to spell? (I personally find it peculiar that the length of the vowel may change in various forms of one word, but that's a matter of remembering a word, not of being able to write down a word we know). Are there some words with vowels pronounced long and written as short, and vice versa?
Btw, remember that there is still English and Irish and THEIR orthographies.
And, personally, the most difficult thing to me, apart from remembering where it's í and where it’s ý (and sometimes distinguishing between "i" and "e" at listening tests), is remembering the voiced/unvoiced stuff which is written differently in Czech and Polish in words consisting of the same morphemes.
zpráva - sprawa (case, matter), z prawa (an old-sounding version of "to the right") (this one is actually easy to remember)
s/z - in Polish both are "z" so every time I have to type one of them I have to stop for a while to remember which one I want to use.
Regarding long and short vowels: Czech people don't find them difficult to spell at all, the difference in pronunciation is absoutely clear to everyone, hence it's also clear how to spell them.
That said, there are a few words that some speakers pronounce with a different quantity (length) than standard. For example "kultura" may be pronounced as /kultúra/. Verbs like "nevím" or "prosím" in the 1st person singular are in casual speech often pronounced as /nevim/ and /prosim/, but not written/said this way in standard Czech. My dad (Southern Bohemian) used to say /lekárna/ instead of "lékárna". One vowel that defies the nice short-long pairing of other Czech vowels is "o" - it only exists in the short form as a phoneme, long "ó" only occurs in interjections and loanwords, it never changes the meaning of the word, and it's pretty much optional: both "citron" and "citrón" or "balkon" and "balkón" are used - in speech as well as in writing.... "hodně" means "very" or "a lot of", and "hódně" (especially just in pronunciation) means "very very" or "a great lot of". :)
There are also (rather small) North Moravian and Silesian dialects that have reduced or lost the distinction of vowel length because they are closer to Polish.