There is tension on both IL axes, but both DH and I make an effort with our respective ILs, while sharing observations aside to each other about "your DM/DF", so it seems to be all right.
On the other end, I know my mother sees DH's faults, and my MIL is frustrated by my non-hypochondriac attitude (on DS's behalf), which I paradoxically ally with strictness (how could I be so unfeeling as to deny him something he's crying so hard about?!).
Both my mother and DH's parents have invited the other set around, and presents are exchanged, etc. Basically, we are all trying hard to get along.
However, I admit that the feelings could be warmerand more natural, which is a bit sad. Mind you, DH, his brother and his parents are often shouting at one another, and taking the piss (not always nicely, either), so I don't want that, either!