I actually like the sound of Montserrat (and have even come across a couple in real life).
But... I keep seeing "monster rat" in this spelling. For this reason I prefer the spelling Monserrat (which I have not come across in real life).
Don't know what to think of Montse, though. As a nickname it makes sense. It's just so unlike what I'm accustomed to. I'm pronouncing it MON-sə as I think that sounds more attractive.
***
Please rate my personal name lists:
www.behindthename.com/pnl/69381www.behindthename.com/pnl/69381/117507www.behindthename.com/pnl/69381/109399hwww.behindthename.com/pnl/69381/132018http://greens-end.myminicity.com/