I noticed how any impact I use has a little 'wobble' in the bit. Really noticeable in a long Philips or a spade bit. I own a Ryobi, but I have used Rigid, Bosch, and Dewalt. Every one with the same thing. Is this meant to be? Will it cause problems when driving screws into my projects?
I'm going to address the "what advantage would there be over a regular drill" part of the question first.
Impact drivers are much better at driving fasteners, drills are much better at drilling. (Hence the different names...)
When you're drilling you want a thin, continuous cut. This means that you normally don't need a ton of torque, but you want it continuously. Drills are built to do this because they just turn at full torque the whole time.
With a fastener you don't really care if you stop and start, but you want as much torque as possible. So an impact driver applies more torque, but it does it intermittently (hence the "clicking" when you use it.) This also has the added benefit of not causing "reaction" torque, when a drill binds up and tries to twist your arm. So you can apply a lot more torque with an impact than you ever could with a drill.
All that said, since an impact is intended to be used with fasteners it doesn't really matter if it wobbles. You're normally using it on something that isn't prone to walking around like a twist drill bit does.
In my experience impact drivers have a short head with a short hex-shaped recess to receive bits and drivers, where a drill has a chuck with a much firmer grip on bits. Hence the greater wobble factor using the impact driver. An impact driver is great for rough framing where I am not predrilling for screws, but I do not use it on better quality woodworking projects. For me it is like the difference between a broad heavy masonry chisel and fine woodworking one. Different tools for different applications.
An impact driver is primary a single purpose tool for installing or removing threaded fasteners, at this it is very good. Much less striped heads or broken screws, and less torque on your wrists. In short if you drive screws you need one. Ditto to most of what was said above but I use mine for all screws.