Testworld with forestry and buildcraft update and the additional mod of Thaumcraft 3 appears to be functioning fine from an in-game perspective. And as far as I can tell testworld instance is not trying to claim too much of the server resources now that furry has rejiggered the settings. So unless furry or anything has noticed anything that could be a problem, we can update soon.
However, not specific to new mods, I did notice one issue with tethers. At least on the testworld we've exceeded the number of loadable chunks, or at least what forge refers to as "tickets". Max is 200 in the config, and testworld is at 208. The server message was something to the effect that chunk requests over the 200 will be ignored. Which might explain by Nine Lives teleport pipe seems to unload from time to time despite there being a tether nearby.
We may have to perform a self audit and eliminate all but the most essential tethers and quarries. ( I'm not sure if any other objects force chunkloading.) Of course, we could try increasing the allowable "tickets" and see how that affects server performance first.