Is it a bad idea to replace pull-up resistors with hard pull-ups?
The idea of pull-up / pull-down a signal is that the signal is being pulled high or pulled down low most of the time, but can sometimes be pulled down or pulled high respectively.
In the case you want to pull down a signal incidentally that is pulled up most of the time, you want to use a pull-up resistor to prevent huge current drawn from the supply.
So, if your circuit really uses pull-up or pull-down resistors as described above, don't remove them. (For example, when a pin is open collector.)
If in your circuit a signal needs to high or low forever (when the supply is present) and no other component can change the state of this signal, then you can hard-wire it. Those signal are not called pulled-up, but high, and, respectively not called pulled-down, but low.
I asked a similar question on the EEVBlog forum some time ago. I had this idea in my head that any signal I needed permanently low I would tie hard to ground, and any signal that I needed permanently high I would tie up via a resistor.
I didn't really know from where or why I used this scheme, so I asked about it. I think it may have been something that I picked up somewhere that was more applicable in the TTL days.
EEVBlog - Pull-up resistors - technically necessary vs preference?
The general consensus seemed to be, and as Huisman suggests, unless you need to be able to pull the signal in the opposite direction, you can simply pull it hard up/down.
It is worth noting that my question was in relation to CMOS-based devices - it may still be applicable/necessary if you are playing with TTL families.
More technical reasons revolved around noise immunity, especially if your pull-up resistor values were of a high value.
As I am writing this, other reasons I can think of for wanting to use pull-up/pull-down resistors might include troubleshooting abilities, "hidden features", or debug/service mode selection for example.
Since that thread I am no longer using pull-up resistors unless I need them functionally.
The answer will be in the datasheet. If the logic input operating voltage specification includes VCC or V+ then connecting directly to positive supply is OK.