The phone does run smooth -- no doubt there, even with the preloaded bloat.
Personally, I want root for so many other reasons:
- changing the SD card cache size and other props
- tweaking memory auto-killer (min/max free values)
- overclocking
- titanium backup
- nandroid backups
- screen caps
- SMB/CIFs-enabled kernels (for video streaming)
- Chainfire kernel mod to add Tegra 2 instruction emulation to non-Tegra devices
- tethering (I have an Android tablet that does WiFi only)
- theming/customizing the UI (custom ROMs, etc.)
Plus you get other benefits when rooted -- typically next-day ROMs for the latest version of the OS rather than waiting weeks or months for an OTA update (and even if you're lucky).