If you have a 2-computer system, with VSL's Vienna Ensemble PRO 5 you can now put Nebula on your slave PC and have it all controlled from within your host computer project (VEPRO sends the audio back and forth via LAN from within host effects tracks).
I have an iMac with a PC slave and this is working wonderfully now with no extra latency - I have VNXT's beautiful EMT140 nebula reverb on an effect Send during tracking and it's working fine with no glitches. It is far more efficient than the current version of Nebula Server. The only advantage of Nebula Server I can think of might be having the GUI on your host, but I'm using Microsoft's Remote Desktop Connection for Mac to have a full screen PC window open, which is very easy to switch to with a key command using OSX Lion's Spaces, so you don't need the local GUI.
I tried this too. But in Logic, it forces Logic in live mode, which makes it unusable since only one CPU core is used. In Reaper i got glitches as soon as i added native effects to the project. Then again, i'm only interested using it with a minimum of 32 channels. What DAW are you using?
Only bummer is that you can't run channel inserts and have them returned to the channel.
For instance, let's say I want to insert a Nebula console preamp(or ANY insert) on a channel, and want to use VE PRO and Nebula on the slave to generate the effect. It sends the signal to VEPRO and Nebula on the other machine just fine, but it RETURNS it via one of the VE PRO outs instead of back to the channel, so the returned signal with the console pre on it will now need its own track.
You could still use it (and cram more inserts on the VE PRO slave side), but now you're dealing with the original track and the returned track (with the inserted console pre and/or other FX from the slave side on it). If you now need to bounce stuff, things get harder and harder to keep track of.
I'm really hoping that Vienna fixes this so that it can return the inserts back to the original channel as it SHOULD be, but I'm not holding my breath.
However as you pointed out, for anything using sends (reverbs etc which need their own track anyway) it works great.
I7-2600, 16Gb RAM host machine I7-875K, 16Gb RAM slave machine Win 7 64 bit Cubase 6 64 bit VE Pro 5 Lynx Aurora 8 lightpiped into Fireface 800