Yes, if you're talking about the Anniversary Update (AU) specifically, or are you talking about the W10 upgrade from earlier windows versions such as W7/W8x?? The biggest reason for the freezes is that people don't know about or simply choose to ignore the running of the W10 COMPATIBILITY TEST during the beginning of the upgrade. This app checks for outdated hardware, apps, and drivers that won't work with W10 and therefore will freeze up or hang the upgrade!! I've been telling people this in my local Computer Club since April 2015 and we've now done 3 presentations including 2 hands-on workshops and they are still bringing in computers that freeze up during the upgrade. When I ask them if they ran the W10 COMPATIBILITY TEST or not, they tell me it didn't ask them to!! And they are correct, the Compatibility Test which used to be called the Upgrade Assistant and similar going back to XP never ran automatically (I wish it would!). Microsoft never seems to be able to get the word out that this is a strict requirement for the upgrade. The upside of this for me, is that most home users don't know about it, and those that do simply choose to ignore it and therefore their upgrade fails or it completes but they get lots of weird performance anomalies once the W10 has been upgraded and they pay me to fix it for them. I've got plenty of other work to do such as virus removal, computer crashes, etc. to keep me busy, I'd just as soon have Microsoft make the Compatibility Test mandatory, and if it's not run the user clicking on the GWX flag with little or no knowledge of computers would not be able to complete the Upgrade without running this test and resolving reported issues from the Test first. Many of us in the W10 Insider Program who helped design and test W10 have mentioned this to Microsoft to no avail (just like we did in the earlier versions of Windows).
If you're interested in more on this topic, we've got a few hundred posts you can read through by using the forum search to look for "Anniversary Update" and there are several threads going there to provide further insight on these issues.