I definitely noticed it the other day when the Captain kept the nose in the air longer than usual (with a high nose attitude). The selection of reverse definitely caused a pitch up.
Intersesting, as obviously in the air, an increase in thrust causes a pitch up and vice-versa. The aircraft is rotating around it's CofG ABOVE the engines. On touchdown the aircraft rotates about the MAINWHEELS, located BELOW the engines, therefore reverse pitches the nose up.
I don't think speedbrakes give a nose up moment on the Boeing (I think it does on the Airbus). The lift dumpers obviously greatly reduce the lift from the wing. The centre of lift is obviously in front of the mainwheels, so this should cause a nose down moment. The centre of lift may move forward, causing an incresed nose up moment, but I doubt this is significant. I understand lift dumpers can actually cause negative lift (a downforce) - causing the load on the mainwheels to be greater than the (at rest) weight of the aircraft.