1. Did you like it? What you liked the most? What you disliked the most?
Overall this system is realy nice. A lot of players were encouraged to do something other than they have been used to. Besides this, many other stuff would be possible to do at the same time, like achievements and so. Also what is worth to say that tasks were usually completly different comparing to tasks we have ingame from X time, some of them are kind of unique, what is really enjoyable, that they weren't just to kill X amount of pokes or sell X amount of items/bring to any NPC.
What I disliked? Some tasks, which needed time consuming. I got it that not every would be easy and that's totally fair, but some of them needed hour(s) to do them (like walking on snow for example or catching 5x dragon). As it was an extra thing added to the game, it should bring us fun, but in tasks like these above many people were frustrated and did just re-roll (inluding me). Nice that you gave possibility re-roll them.
2. What would you change/improve in current tasks?
About tasks - for me some need change an amount, like walking on snow, catching 5x dragons (here maybe 1) and others which number is a bit high.
3. What tasks would you like to see added in future?
Like what Fallen Angel said - using X type of moves or certain move, sniffing pokes. Other: harvesting any berry 25/30x (don't know if it was already, never got it), using skills 30x/50x (ride/fly and so), eat any food 30x~, maybe looting X times certain item (that easier ones, not like TM/held or even plate), what are easy to loot (like fire essence), maybe changing items into essences.
In the end would like to propose giving 3/5x free re-roll for tasks. Many things which have been added recently needed diamonds (like gifts, pass and others) - it's ok, but due those things price of diamonds increased insane and that way many people lost posibility of getting premium for in-game money. 3/5 free re-roll maybe isn't something big but would help a lot.
Also thanks for that system, it was fun to make something different!