Pros
Shared hosting is cheap. Really cheap.
Shared hosting is manged - you don't need to be a trained systems admin.
Cons
You don't have much control over the server environment. Some applications won't run, others might not run to their best ability. Did you hear about how cool node.js is? Too bad, you probably can't sandbox it.
You have no control over fixing downtime. You put in a ticket and hope someone takes care of it soon.
The server will be slow when anyone on the server hits a peak in traffic.
Support is generally subpar for shared hosting providers.
If the host hasn't secured the server, there could be security issues where others on the server could get access to your root directory or database.
Scaling? Ha, more like, when you grow you have to find a new server to migrate to and hope the process is fast and smooth. (It probably won't be)
Inevitably, many cost effective hosts will not be in your time zone. Or those near yours.
Suggestion
Shared hosting at the major hosts isn't too bad. If you can't afford the money (remember, this is tax writeoff material) then stick with them.
If you actually need the performance and such, find a way to pay for the upgrade to a VPS or a dedicated. A good dedicated server will be $100/m. You'll need to know basic sys admin stuff, but just knowing Linux in general and being familiar with the services you run (apache, mysql, postfix, php) and how they are configured is suitable.
Also if you are using a panel like cPanel.. your goal should one day to admin your own server without it. You'll be intimidated at first, but quickly find that you are more quickly able to do anything you need over command line.