I well recognise many have had serious issues, and I don't belittle their issues at all.
* * * * *
Worst difficulties I've had:
- understanding / sharing 'lag source' info; once I got it down, it was easy
- the Land Store was broken for a day, once - I'd taken in about $L 200k toward a sim purchase, and was really stuck. Cyn Linden saved the day

- once asked to be a 'judge' of other users in a very 'First Life' serious case.
(I rightly refused, and referred *all* parties to the Company. Being a sim owner does not confer special rights, or superior social insight to 'judge' others by.)
Most fun I've had:
- a zillion new friends! (more than I can keep up with, my only regret)
- the 'creative leverage' thing. 90,000 prims is a lot to work with - you literally NEED a lot of people involved or you aren't going to have several sims full of compelling content.
Most ridiculously fascinating thing:
Port Caledon had the 'phasing' bug for three hours, once. Yep, two instances of Port Caledon, each connecting to the rest of the grid for about a minute, then swapping.
It was like a rift in time.
I was caught in one, not realising - then relogged because I thought I was having 'asset server problems'. I logged back in, but into the other instance - I couldn't find the friend I was just talking to!
Eventually I stepped out of the sim, turned, and saw it vanish to void, only to come right back with DIFFERENT people in it, including the friend.
A crowd gathered on a nearby hill, and we took turns trying to get the word out and rescue the people inside.
I did the secret incantation and dance I was taught to summon the mythic gridmonkeys, and after a while they came. Port Caledon has been stable ever since.

It's been good. Really strange sometimes, but good!