Same here! 

I have the same problem, but on Dell Inspiron 15 5510.

If I install "Realtek High Definition Audio Driver" update, version 6.0.9202.1, my Windows boot up time increas from a few seconds to over a minute or two.

I can live without that update, audio is working fine (except from a small delay when it has to play a sound after few seconds of inactivity), but i'm concerned that one day this Realtek drive update will be forced by Windows Update (today, after a system image restore, it is listed in optional updates)

@Gbent @sandor_otvos can I ask you if your "Fast Startup" option was disabled in Power Options when you experienced this slow startup?

Mine is disabled, but I found some posts here in Dell Community where users complain of a long time to reboot (which does not use Fast Startup), but not for the "shutdown - power on" sequence (which uses Fast Startup, if enabled).

@sandor_otvos this confirm my suspicions: slow boot due to driver update only occurs if Fast Startup is not running (i.e. during system restart, or if Fast Startup is completely disabled in Power Options).

Everything is in default for me, so Fast Startup is ON. Restart got very slow only after last system updates. Did not change any settings. Interestingly, if I turn off the laptop and then turn it on again, startup is fast, but if I restart, it is slow... Come on DELL!

It was disabled

I enabled fast startup and again installed the driver update. Startup from shutdown was fast, but restart was very slow. I went back to the previous version and both startup and restart were again fast.

I have had enough of the slow system restart, so I decided to restore the system using DELL Support Assist. Unfortunately, the system restore completely failed, and Windows won't start anymore. Tried everything to get it back, but no success. I did everything properly, so I do not know what happened. What I know is however, an application (DELL Support Assist), which should help in such instances completely ruined my system, and now I will need to make a complete system reinstall which will take a lot of time! This all is because a poor driver released by the company. Thank you very much DELL, you made my day...

I have had a number of update disasters over the years. For that reason I always make a system backup before I install any updates. In that way, if the update fails,  I can restore the system  to the state right before the update. There are many fine backup programs, but I use Macrium Reflect.

We request you to perform a System Restore to the previous date where the system was working fine and let us know the result of the same.