I, too, like the Arena events! In fact, thanks for starting this thread because I can’t start threads at the moment while I’m in jail 
I have a few reasons for liking this event:
1) I own the right cards.
Not to be underestimated, this one. I see a lot of posts on facebook from people who just don’t own any dragons at all. I own 3, and only Avaricious Dragon is actually any good (he does a great job of sorting out Sarkhan’s poor mana generation). The same thing happened with Gideon2 and his allies.
2) I haven’t had to fight a lot of difficult opponents.
The objectives in the Arena are crazy hard. And, as has been pointed out before, generally counter to the whole ideology of each planeswalker. Sarkhan wants to kill with dragons, Gideon2 wants to kill with Allies. But playing 6 of them and somehow not managing to kill your opponent before then? Not easy at all. Infuriating, sometimes, in fact. I think if I’d been put up against a bunch of Baral decks, or creatureless Ob decks, or Kiora Waterveil decks, these objectives would have effectively become impossible for me in those games, and I’d just have cried. But luckily (at least, I imagine it’s not by design), most of the games I played were against fairly average decks, often with cards much less powerful than mine, and so I had a fighting chance of clearing the objectives. I like challenging more than I like impossible.
3) I don’t care about losing.
The pressure is very much off in this event. The objectives are killer, but the penalty for failing to do them is minute. As such, I devoted myself to trying to get the objectives at every opportunity, even losing games on occasion because I’d shot my own creatures in order to avoid winning too fast, and then been overrun by my opponent.
There are a lot of reasons for this; flat prize structure, bad prizes, smaller brackets, low player interest. Most of these reasons currently apply to EVERY event, but I don’t think that’s healthy. It’s nice to have one event which doesn’t feel competitive, but at the moment, nothing at all in the game feels competitive, and that’s one reason so many people are bored with it and downvoting it in the app store recently.
4) It’s different every time
Variety is the spice of life, and the spice must flow. PvE events like RatC are getting terminally boring now from constant repetition. PvP events like NoP are a bit less boring, my opponents vary, but the restrictions on my own deck building (node color and objectives) are always the same and are quite tight, so I really don’t get the opportunity to vary my decks that much (not if I want to score points for my coalition, at any rate). But the restrictions in the Arena are tight, and (mostly) change every time, making each one a different deck building challenge. Sure, a lot of them are STUPID deck building challenges, but they sure are challenging. There is absolutely no point running that 3rd node exactly the same every time, though, is there?