Just a couple things from my recent experience:
1. I would definitely make sure it had a "fine tune" adjustment for leveling after hanging. The actual mount is often small. Once a larger TV is hung on it, any imperfections become magnified.
2. I would look for a "swing out" option. Some of the sanus mounts have an option where the TV can swing away from the wall after mounting. It makes it WAY easier to add new connections (e.g. plug in a new HDMI device).
These might not be compatible with "inexpensive", but would be well worth the cost in my humble opinion.
Polk Fronts: RTi A7's
Polk Center: CSi A6
Polk Surrounds: FXi A6's
Polk Rear Surround: RTi4
Sub: HSU VTF-3 (MK1)
AVR: Yamaha RX-A2010
B&K Reference 200.7
TV: Sharp LC-70LE847U