I've had Carpathian's for a few years now. All were purchased from Becky's Bees. The majority have been great to work with and forage extremely well which is especially noticeable on cooler days.
Generally they have been very calm around the hive and most often don't need any smoke to inspect, that said, I've had the odd day when they've been pinging off my veil and have been defensive...but a few days later I'm able to inspect them without smoke and they hardly pay me any attention at all! These contrasts in behaviour have been on days of near identical weather and there has been no obvious reason for them to change. That said, it's only happened a few times a year and overall they are great to work with.
Compared to the Carniolan's that I've worked with over the years I'd say that they are a touch slower to build up in early spring, but their honey harvests have ended just as high perhaps because they build up colony strength very quickly in early-April. I have read that their harvest is slightly lower than Carniolan's but can't notice any significant difference personally.
Quite remarkably, they've yet to have shown any significant signs of swarming! From memory, I've only found around three or four 'play cells' over the years. My bees always have room to expand though.
