Best things...
Dimmable touch lamp - didn't have to fanny about finding a switch, and could keep the light dim for night time feeds and nappy changes.
Bath seat - handy to put them in something to support them while having a bath - though they don't really need baths when they are super new
Caddy - I had a wee caddy thing that I could put my phone, water bottle, multi vits, nipple cream, snacks etc. Meant I could easily shift all that stuff elsewhere in the early days, e.g If I decided to sit and feed or hold baby for naps elsewhere in the house.
A baby seat thing at dining table height - had this in the kitchen, handy to have somewhere to put baby when cooking or when me and DH wanted to eat together, but not put baby in buggy and have to keep leaning over to check he's ok, did have a place to put sleepyhead or playmat in the kitchen so this was a life saver.
Worst things...
I can't remember lol. I was a sling fan, bought a cheap fabric first, loved it, then bought baby bjorn.
All the best OP!