I can't help you with the "ugly interface". The other contributors have already given you some insight into your other concerns. More specifically, the model 2500 STB is the slowest that Verizon still offers. This model is slow when navigating the Guide or On Demand menus. It often stores up remote commands while seeming unresponsive, only to execute them rapid-fire later. It can even grind to a halt when using the On Demand menus. But most of the other models perform moderately well or better.
The model 7100-P2 is smaller and has no front panel clock. And Verizon hears no end to the complaints from people looking for the clock that is no longer there. Perhaps if they created a better tracking system so that people like you could get this model and everyone else could get one of the others.
Here's the one thing that I can help you with. You can turn off the front panel clock. There are two settings that control this function. The first controls what the display reads when the STB is on. The second controls what the display reads when the STB is off. Follow these pathways:
Menu > Settings > Set-Top Box > Front Display > Show Channel Number > OK
Menu > Settings > Set-Top Box > Standby Front Display > Turn Display Off > OK > Exit
Furthermore, if you want to make the box disappear altogether, you can look into IR extenders that would allow you to hide the box somewhere out of sight (as long as it is still well ventilated), and control it through a repeater mounted near your TV.
Finally, there is supposed to be a whole new system coming out this year to upgrade the FiOS TV hardware. However, Verizon has still not revealed a release date.
Hope this helps