I'm so glad you asked this question! I'm going to be attending pharmacy school next year and I worked at a compounding pharmacy this past summer (40+ hours). I absolutely loved it! The night I was hired, I started working immediately. As a tech, you do most of the compounding...we compounded gels (lotions), troches (lozenges), suppositories, injectables, capsules and suspensions. We have a database that stores all the formulas we've ever done and since the pharmacy I worked at just opened, a lot of the times, I had to calculate and enter in the formula myself and then the pharmacist would check over it before I started making the product.
Then I'd measure out all the ingredients (kind of a pain when you are making out small quantities because you have to measure EXACTLY 0.2550 gm of stuff). Mix them, and finish the compound. It was tons of fun because it was such a hands on experience.
However, as a pharmacist working in compounding...it's a bit different. The pharmacist doesn't compound as much as the techs (in my pharmacy) but he still compounds some when we were backed up (since it was just me and him for a while). He does all the injectables, however, because those have to be completely sterile or someone could die (if it's contaminated...which is what happened a while back and gave compounding a bad name). My pharmacist also looked for different ways to improve our formulations to make them more user-friendly. He also marketed a lot to physicians offices in Houston (since this was his own pharmacy). He worked with nurses and doctors a lot to ensure that the patient was receiving maximal care.
Now, to answer some of your questions, it does not take extra schooling, but I think you have to certify in a few things like if you want to do sterile injectables...Also, if you want to open up your own compounding pharmacy, the state board most likely requires more stringent requirements.
I'm not sure what the pay is like, but it seems like it's an area that would be harder to find a job unless you want to open up your own store. And even if you do that, I would recommend working in a compounding pharmacy first so you know exactly what is going on and can learn a few tricks of the trade. I know in the pharmacy school here at UT Austin, there is a lab on compounding but I'm not sure how much further it goes than that. Also, students at the College of Pharmacy in Houston get to take their lab at PCCA (Professional Compounding Centers of America) which is the bigggg compounding source for nearly all compounders. It's a great place!
Sorry this reply was sooooo long, but hope it helps! Feel free to ask me any other questions and I will try to help. But basically, I am also really interested in compounding as well...if anyone else has any comments, feel free to inform me! =)