Just like the TARDIS, the Switchblade + is smaller on the outside. Very small indeed. Some might find it too small - I'd say try it first. It is robustly built in the typical EH die-cast case, with bright LEDs and conveniently placed foot switches and promptly labelled ins and outs.
The Switchblade is a channel selector - it sends the input signal to channel A, B, or both. There's a tuner output as well - if you don't need to connect a tuner, you can use this to output a separate channel; however, be warned that it bypasses the Switchblade and cannot be switched on or off.
The left foot switch toggles between output A and B. The right switch runs both outputs in parallel. When the right foot switch is engaged, the left one is disabled, which makes sense.
The unit is completely passive and works without electricity. The LEDs, though, need juice to show what's on and what's off. They consume so little that a 9V battery should last ages: EH, however, have added a DC-in socket. Nice touch, but unnecessary.
The Switchblade is true bypass, as you would expect from a product of this type.
They say it works if you reverse it (channel A and B become inputs, and the input becomes an output) but I haven't tried it.
On the whole, Switchblade + turned out exactly as I'd imagined. It isn't a unique product but does what it says on the tin and does it well. Besides, it is priced very reasonably. Recommended.