Our experience:

• Create a portal-pair
• Place gates across the portal (to prevent livestock from crossing
• Walk through portal.

EXPECTED: In previous versions, one arrives standing in/on the portal and can open the gate, step out, then close the gate behind them.

ACTUAL: starting in 1.8.1, arrival seems to be offset by 1M, which can result in unusual or disastrous placement.

More details:

Scott emails the gang:
The server was upgraded [to 1.8.1] last night, and it seems that it may have caused a vertical shift in the Nether. Both of the portals at my main camp (Cathedral Rock) will port you to a spot about 4 meters lower than expected. Unfortunately, there is nothing there, except a very long fall. In one case, the fall is ended by lava.

Bottom line: exercise caution when using portals. This situation may be unique to my area... and it may have nothing to do with the update. I just wanted to let you know that I had these issues this morning.

[Then, later]
The issue I had this morning seems to be caused my a new [in 1.8.1] behavior when going through portals. Instead of delivering the character to the portal on the other side, the game will deliver the character to a spot one meter in front of (or in back of) the portal. If that spot has a "closed" gate, the game will likely deliver the character to a lower position.

Solution: keep the space one meter in front of the portal empty.

Josh (server admin) says:
That seems a rather odd change to make. Any clue which side is the front? I’ve certainly set a lot of portals against walls.