My family and I have gone during Easter, summer, Thanksgiving/Christmas...but we had our first Halloween trip just last year. And, I have to tell you, it was awesome! Definitely something I will remember forever! Halloween is my favorite holiday, so to experience my favorite place during that time was something I had dreamed of for a very long time. The temperature was a bit hotter than I expected (and quite different from what I'm used to during that time of the year here in KY). And something I did NOT take into consideration when picking out a costume for the party (we're talking shorts and a tank top UNDER a full robe and hooded cape, wig, and fully painted face...everyone loved it, but I was BURNING UP...I certainly gained even more respect for the Disney characters that day). The only weather-related thing you really have to worry about is torrential downpours. We experienced one every day (sometimes during the middle of the day, sometimes in the evening), but they only lasted an hour. Course, we went earlier in the month...you may have better luck going late Oct.
BUT...you HAVE to experience WDW during Halloween at LEAST once! I'm 23 so, unfortunately, my inner child rarely comes out to play any more. But I was totally dancing and singing during both viewings of the parade (my family and I generally aren't "parade people", but we loved it so much the first time, we HAD to see it again) and after. The fireworks were great! The trick-or-treating was...just..AWESOME! Seeing Disney-fied ghosts randomly walking around the park...the Liberty Sq. lantern lights being eerily green...the buildings being lit orange, red, green, and purple. The whole place just took on a whole new atmosphere...and I LOVED IT!!!
AND they sell special pins and t-shirts during the party only...so it was fun collecting all that, too.
Good luck with your planning! :wave: