In the older versions I'd always use knock to get in to places unnoticed or when we didn't have enough skill to open them conventionally (notice I'm talking about 3.5 since Next is obviously going back alot farther than 4e which was just wierd). The changes to the spell are a bit much.
- New spell does 1 lock or impediment , old did 2.
- New spell cancels Arcane lock or hold for 1 minute, old did 10 minutes.
- New spell makes an noise audible over 300ft, old spell had only verbal component to hear.
- New spell has somatic components, old spell didn't. This isn't listed explicitly for the new spell, just the flavor text.
- New spell has range of 50ft, old had 100+10/lvl.
- New spell can only open locks up to DC 20, Old spell didn't have a DC limit, nor did it have a check.