I recall there being some issues with the first generation of Campy batteries, but that's about it. I suppose for both Campy and Shimano when they work they work and when they don't they don't. That's the trouble, it's an on/off thing with electric. I've built and used both Shimano Di2/Mechanical and Campy EPS/Mechanical. With either group, I just prefer using mechanical. If I was maintaining a team of bikes, then electric would make my life very easy, for the most part. I find Campagnolo stuff to be really well made and machined, especially when it comes to their cranks, bearings, and cups (barring some early versions of the cups for some pressfit shells). And their chains and cogs are really jewels of precision imo, and durable too. I always measure the cups diameters (outside and inside) and the bearings and it's always a perfect fit and is the reason my first BB choice for a campy install is always Campy cups. The shells of the frame BB's are more susceptible to variations, but you know what, despite all the horror stories (and I've certainly worked with a few) with a proper install I have never had a problem, even in the Cannondale's that I've "fixed" and that includes installing SRAM BB's into Cannondale shells. Done right, they work. Getting the "done right" part is the tricky part. And that was certainly a lot easier in the days of threaded BB shells.
My favorite group is for sure Campy Mechanical... pick one (SR, Record, or Chorus), just pick your price point. The thing is, the difference between the Chorus group to the Super Record group is far less in terms of function and quality than it is between Shimano 105 and Dura Aces. The brakes are a good example. I have 105 brakes (new version) on my rain bike. The flex and fitting of parts is noticeably less tight and more "flexy" than on Dura Ace. I will be swapping them out to Dura Ace 9100. Maybe they build to different levels of manufacturing "tolerances" between the groups, whether on purpose or not, I don't know, but it's noticeable.
But if you look at the difference between Campy's Chorus and Super Record line of brakes for example, the differences are far less functional in nature and more about a few little niceties added or a few grams shaved, along with a disproportionate increase in price, ouch. A few ti screws, some nicer adjustment capabilities, but as far as how they work or function, I'm fine using either. I have Chorus brakes on one bike simply because they had slightly more clearance than the Record or Super Record. But functionally they are perfect. Other than brakes, the CULT bearings of SR cranks are the best in the biz as are the same bearings in their wheels, so that is a significant difference for sure, but you pay for it. But functionally, I don't think anyone would be crying over a lack of performance from Chorus vs Super Record.
Plus, I can shift a mechancial Campy group far faster with more control and have every option available to me all the time. Much moreso than I can with either of the electric groups (Shimano or Campy). Shimano mechanical is very smooth, but I still can't shift to all the options as quickly as I can with Campy mechanical. By that I mean simultaneous front/rear shifts WITH the ability to shift 1, 2, or 3 cogs in that same simultaneous moment with the same motion. It just becomes engrained, through a tactile feel of knowing exactly the right pressure/feel to enable a 1, 2, or 3 cog shift at the rear along with the front. It's essentailly instantaneous compared to any of the other options. You could even do more than 3 cogs at a time, but I find I'm never in a position where that's necessary or desired. Basically any option that you could configure in Shimano Synchro, Semi Snychro or Manual is always avaialble to me with Campy mechancial, any time, that instant. And I just enjoy shifting a perfectly tuned mechanical system far more than the sterility of a button push. I installed EPS on a guys bike because someone told him it was so much faster, etc. It's not and I told him that, but we put it on anyway. He has had many Campy bikes so can tell the difference. He eventually said with respect to EPS, yeah, it's not faster if you're familiar with mechanical, but it always hits the shift... but mechanical is "funner"." I completely agree... mechanical is "funner", and I will never have to plug it into anything or worry about it being charged enough.
So yeah, thats my 2 cents... Campy Mechanical... Chorus, Record or Super Record pick one.