A good cutter is definitely worth it. I've found the biggest difference to be just going from a cheapie to something decent though. Xikar cutters are nice, but they don't work that much better than the $20 Cuban Crafters double guillotine I had before I got my Xi3.
There are other nice cutters around too. I know a guy who had a Xikar, broke it, and decided to give a Credo cutter a try while his Xikar was out for repairs. He liked the way the Credo worked better, though he often still carried his Xikar since it was a lot smaller.
On a good day a shop will have a few different kinds you can play with before making your decision.
If you've got one of those Cuban Crafters double guillotines that are held together by a bunch of little screws keep an eye on the screws. My former local B&M back in Chicago quit carrying them because they got too many complaints about the screws falling out.