I had it done 10 years ago, had I think 18 or 20 trays? I was told initially that I might need an extra few sets but I didn't.
I had maybe 6-8 attachments quite early on, and filing afterwards which improved the look immediately. My Invisalign tech said because of my teeth I would only be able to get 95% straight unless I went for surgery and I was happy with that over fixed braces as my teeth made me very self conscious so in my head any improvement was good. I was also getting married during treatment and didn't want fixed braces in the photos.
After treatment I had a fixed retainer to the front 6 top and bottom and I still wear a plastic retainer for the top every other night. I wish I'd known this before but I'd still have done it.
I found it painful for the first hours of each new tray so I swapped my trays at bedtime so I could sleep through this bit, then usually it was fine enough by the next morning. A little sore but I could eat nearly normally.
The attachments felt quite sharp initially but never caused an ulcer I don't think, and were usually covered by the trays so they acted as a buffer. Any changes I got quickly used to.
I was more aware of how I spoke differently with my trays in, though people I spoke to didn't seem to notice. I hadn't noticed others either, I had a meal with someone a few years after I had my treatment and he took his trays out to eat, it was only then that I realised he'd been wearing them and I'd known him for a while.
A small faff was carrying round a toothbrush and paste to clean my teeth before I put the trays back in at lunch. It was probably good for my diet, I didn't bother snacking as the faff was too much!