I suppose they can be useful, but I prefer to download them myself. The only benefit they have is if you have one version of many of a certain peace of hardware that's tricky to differentiate (I.E; physically looking) these often see which version is any relevance for you.
To be honest, not that many people actually bother updating drivers unless they have some sort of issue; despite the fact that with some updates comes with slight performance and/or stability improvements.
As far as your problem goes, I doubt any driver update will speed up your system with much noticeable difference. Windows naturally gets slower the longer you go on your current install because of lots and lots of "little things". Your registry naturally "grows" and gets more and more fragmented; Windows has a tenancy to try and "speed up" accessing programs you use often, the problem with this is that it's always "learning" what you use and as a result it constantly caches more and more programs (ironically slowing it down) over time; various data files like Index.dat grow considerably over time too causing added slowness with anything that depends on them; your services grow over time just like your system run - only this is harder to control because of dependencies etc...
If you want to truly speed up your system (or restore it to how it was) the best thing you can do is reinstall Windows, I actually do this every so often because of this reason (around once a year, maybe longer). Microsoft aren't known to write the most efficient software, and on top of that Windows has got more complex over the years so this the advice I'd give anyone experiencing slowness.
