HTC slider appears in FCC filing
The device features a touchscreen, along with a full QWERTY keyboard. In the US, it's got support for AT&T's 3G bands, and there's four touch-sensitive keys below the screen for home, menu, back and search. There's a blue plastic trim around the screen, and around the edges of the keyboard.
Beyond that, there's very little detail on the ground about what this phone is. Thankfully, it doesn't look like it's too far off market in the US, but whether it'll come to the UK is yet to be determined - HTC often maintains almost entirely different lineups on the opposite sides of the Atlantic.