25 hours in (non-spoilery keywords: Welcome to the Jungle), I can say that the answer is an unequivocal NO. I love this battle system. It's the best one ever. Let me tell you why.
1. Hack-and-slash battles run themselves. Once you've set your basic attack and heal gambits, you almost don't need to touch the controller unless you get into trouble. Your leader will run over to the nearest fiend and everyone beats it up until it dies. Simple as pie. Easiest. Leveling. Ever.
2. Party flexibility. I love, love, love being able to open the party menu and make changes on the fly. That weapon not working out for you? Need to upgrade someone's HP or strength? Basch is on the verge of death and a black mage would do you more good? No problem. You don't even have to wait for his turn, as you would in FFX. You can even swap out someone who's been KO'd. It's awesome.
3. Character flexibility. Anyone can be anything, wear anything, wield anything. No more of this "here is the magic user and here is the warrior and here is the thief." You don't have to play weird games to get a bunch of mages or thieves or whatever you like. Create funky specialists or raise a pack of generalists or do a little of each. It so cool, being able to put together a party that fits your gameplay style. (We're mostly going the generalist route, with a touch of specialization thrown in.) And if you need to change gears in the middle of a battle, you can. (Have I mentioned how much I love being able to open the party menu during battle?)
4. Quickenings. I owe everyone who warned me to start using quickenings, and how. They're like the overdrives of this game, but you have so much more choice about exactly when you get to use them. No keeping track of funky gauges! You have all your MP, you can use a quickening. Want one single piece of advice for making this game easier? Get a quickening for each character ASAP. You will save yourself so much trouble with bosses and some of the tougher fiends. Seriously. Just do it.
So. I am a believer. I'm sure I could come up with things I liked better about the FFX system if I tried, but so far this comes out the winner in so many more categories that I am happy to throw it my full support.