With great specs, solid build, and reasonable pricing, can the Tamron hold its own against Canon & Nikon's pricier rivals.
This is an issue I cannot stress enough. You must be diligent about backing up your photos, videos, and other important data, especially if you are using that information professionally.
ISO can be a very important tool in digital photography. It allows you to capture great images in low light when used properly, yet without a firm grasp on the limitations of your equipment, it can very easily ruin your photos. Most digital cameras allow for manual over-ride of auto-ISO. Learning to master when and how to use ISO will be an important step to improving your photographs.