We all root and use modded roms for various reasons. Some want to explore the newer ideas and try the latest cool roms at will. Others, including myself, want a good, stable rom with lots of custom options. After a few weeks of tweaking it, I just go back to using the phone. Both are fine approaches, it depends on what you want. The first option, with easily swapped roms, is not going to happen with the S4. The second, works just fine with the Hyperdrive mod. I agree that the S4 is a great phone, I did root it, I like Hyperdrive, and I use the WiFi tether routinely.
The advice is this: If you want to choose from a variety of roms, especially if you want an AOSP rom, you'll be needing to have an older S4 or another phone altogether. If you're content with the one or two custom rom mods available for the newer S4, such as Hyperdrive, you'll be fine.
