Premiere Pro is useful, but not user-friendly (even just starting a new project will require a bit of research). Premiere Pro CS4 and CS5 and Premiere Elements (versions 7-9) can handle AVCHD files (the earlier versions cannot). Therefore, you would not need a file coverter.
Premiere Pro is expensive (700-850 USD), but if you are a student or teacher you can get a big discount. CS5 only works on 64-bit operating systems. If you have a 32-bit system, you would need to get the CS4 version.You can download a free trial version of Premiere Pro to test it out. Premiere Elements is a lot cheaper.
If you are working with a Mac, you should probably be looking at Final Cut Pro.
I am using CS3 at the moment at school and CS4 at home (along with similar Canon camcorders). The benefit of using Premiere Pro is that you can use it in conjunction with other Adobe products (e.g., Photoshop, Illustrator, AfterEffects). The software can all be bought in one package (Master Collection). At school, we work on a wide variety of mulitmedia and design projects, so this is a suitable set up for us.
If you don't need those other Adobe programmes, you might consider Premiere Elements. You can also look into Sony Vegas/Sony Vegas Pro. These programmes are good quality and offer nearly as many functions as Premiere Pro, but cost a lot less.