At this point, Windows 10 has been available for just over two-and-a-half months, and overall, it has received a warm reception. In those mere months, there have apparently been over 100 million installs, so if you're holding out on upgrading due to fear of issues, that should help instill a little bit of confidence.
In my personal experience, upgrading to Windows 10 was an absolute breeze - if you ignore the fact that I had to first remove a Linux install from my main drive first (backed up, restored after-the-fact). It was actually the first upgrade experience I had with Windows where I couldn't find a single issue when first arriving at the new desktop. Everything simply worked, including applications that have generally always needed to be reinstalled to function properly (VMware Workstation, for example.) Overall, it's not hard to see that Microsoft worked diligently to make sure the upgrade process, or even fresh install process, would spawn as few issues as possible.
So now, with the launch out of the way, and people enjoying the OS, we can now look forward to future updates. According to Paul Thurrott, we're not going to have to wait long. At some point in November, Microsoft is said to be releasing "Threshold 2", a big update that isn't a new build, but rather a cumulative update. Officially, Microsoft refers to this as "Windows 10 Fall Update".
There isn't a big list that tells us what's en route, but we are given some teasers. There will be an updated version of the Media Creation Tool, which I find a bit interesting since the current one works so well, updates to Cortana, as well as enhancements to Edge. Unfortunately, those enhancements do not involve add-ons.
Here's something that's bound to please many: "Windows 10 Fall Update will support activating with your PC’s Windows 7, 8, or 8.1 product key. For this to work, the key must match the edition of Windows 10 using the same upgrade matrix." This is something that should have been supported from the get-go, so it's nice to see it being tackled.
When the update becomes available, it will be downloadable through Windows Update. If someone installs Windows 10 RTM fresh, WU will update to this Fall Update right from the get-go, without requiring a slew of prerequisite updates first. See? Microsoft is actually paying attention to our complaints.