Mid-september 2014. Weather was rainy some days before and it was really hard to decide do the climb or not reading all those whining off-season reviews. But in the end we decided to go (no, srsly, to be in sri lanka and not to climb Adam's peak is like to be and sri lanka and not to buy some fine tea).
Looks like we got extremely lucky - sky was clear all night, bright stars, no rain, no fog, yes the wind is blowing - but it's a mountain, what do you expect, take some windproof jacket. You will be totally wet at the top too so take a spare dry t-shirt with you.
There were like 10 more guys with us - all tourists - so no crowd like there is in season.
Started at 2:20, finished at 5:10, sunrise was at 5:30 or something like that. Views are absolutely stunning and worth every step of that goddamn ladder (I hated all ladders for like 3 days after that climb). Sunrise is great but morning views when mist starts to go up are even better.
Go for it, and you will be rewarded.