I like it quite a bit, but don't think I 'love' it... so I guess I gotta vote neutral lol
I generally like collecting them, but have never used one on a team.
They could do all manner of things with them... like for example have a dungeon where what paths open to you depend on what combination of 3-5 Unown are in your party (with the box access from anywhere we have nowadays 5 shouldn't be a problem... just leave at least 1 slot for an actual mon for catching/fighting stuff).
The little Unown scavenger hunt in PLA was pretty fun, but did not really do much of anything for a reward.
It's a pity it doesn't evolve into Sigilyph despite it looking like an Unown battleship with a different eye color. Could've like made the 'head' the letter shape.... would required 28 forms of Sigilyph though lol