According to early Nokia 6 performance benchmarks, the Nokia 6 does disappoint. gsminsider posted an image of Antutu and Geekbench 4 benchmark test results and the Nokia 6 scored 44,564 points in Antutu benchmark app and 636 single-core score and 2672 multi-core score in Geekbench 4. Just to remind you that the Nokia 6 uses the Snapdragon 430 processor, which is a low mid-range processor and the results clearly shows that the Nokia 6 even struggles to compete against some of the other mid-range smartphone as far as its performance goes.
Just to keep things in perspective. I took the results from various benchmark website, so they might defer slightly from what you get with your own device. The Sony Xperia Z5 scored 51,627, HTC One M9 got 56690, Huawei P9 received 50,556, Honor 6X got 56025, Huawei Honor 7 got 53045, Xiaomi Mi5S scored 121,407, etc. As I mentioned, the score may vary but it gives you kind of a idea about the relatively low performance of the Nokia 6 compared to other mid-range devices.
The Snapdragon 430 is a low-tier of the mid-range processors and many people would have preferred to get the Snapdragon 652 or the 653 ones which are newer and more powerful, especially for a mid-range phones in 2017.
You need to ask yourself whether to get the Nokia 6 or wait for February when Nokia is expected to release even more powerful smartphones. I personally would prefer to wait and see what other devices are available, analyze their differences compared to the Nokia 6 and then make a decision. Some people even don't have this decision because the phone isn't available in their country (only in China and Philippines) or don't intend to import it. I think that the upcoming Nokia phones will be much more powerful and will be available globally, so I think it's worth waiting for the announcement of those new phones.