I own one, for winter riding (A Shimano Alfine, 8 speeds). And an IGH is:
- More expensive than a regular derailler
- Heavier than a regular derailler
- Has wider spaces between the gears than a regular derailler, and also has the same or less total range over the gears
- Slightly less efficient than a regular derailler

IGH's are interesting. And if you combine an IGH with a belt drive, you have lower maintenance and that's pretty cool (also kind of expensive in upfront costs though).

But, in my opinion, not the direction you want to be heading from your description.