Yes it does affect all portals. New ones, old ones just the same. We also use a tunnel network near the top of the nether, and the greatest problem are people suffocating in the walls because of the portal exit displacement.
Confirming this. Installed the pre3 build on my server and its putting players in the walls. Doesn't matter whether they're using the 1.8 client or the 1.8.1 pre3 client.
Building new portals didnt fix this.
Delete your 1.8 profile and re-download.
Not a bug.