When I took the first looks at english grammar, I felt quite relieved to see that the grammar itself was much more friendly than italian's.
Seeing it in reverse, I can understand what can be troubling for those who use English as primary language.
First of all the verbs. In the english language, apart from irregular verbs, the forms and tenses are much more straightforward. Unfortunately the situation in italian language is quite different: there are so many "Modi" and "Tempi" that could easily scare a student at his/hers first approach to a foreign language.The fact that (with only a few exceptions) every "Persona" has a different suffix, makes the situation even worse. Its a matter of fact that a good slice of the italian population cannot coniugate the verbs correctly, and a lot of those who can, probably cannot identify the correct Modo and Tempo without thinking about it for more than a few moments; of course this is directly correlated to how much time has passed from schooldays. Historically the verbs had led to many jokes, especially about the use of "modo Congiuntivo" and "modo Condizionale", the most notable of wich is Fantozzi's italian: in the Fantozzi movies, nobody not even scholars, could use the Congiuntivo correctly.
Another funny thing that an english can stumble upon is the "sexization" of words. When I approached english, I felt really happy for not having to memorize or to think about the sex of spoons and forks (i.e. IL Cucchiaio è maschile ,LA Forchetta è femminile)

. For people coming from a language whose only articles are "the" and "a" and the words are, more conveniently, all neuter, italian may seem alien at least. Many foreign girls I girls I met in the past, found the italian words very cute because they ended in vowels and they liked how they sounded. I used to smile and tell them (in my awfully slow and clunky spoken english) that unfortunately those vowels weren't there just for cuteness but in general they were used to specify singular/plural and gender of the word itself.
Am I right? Of course my point comes from what aspects of the english language i found easy compared to italian, so I'm not saying that this is truth, it is... some kind of speculation. What else do you find difficult?