Lagging compared to what? Lagging compared to some other remote desktop system? Because if you can show me a remote desktop system that is faster and less laggy than NX 4 I’ll be glad to spend some time learning how they did it.
Or do you mean lagging compared to NX 3? If it is lagging compared to NX 3 when running lightweight X applications like a terminal or an IDE, then I’d say that it’s rather normal. You can’t compare NX 3 to NX 4 in this respect. NX 3 is simply unbeatable at running such X11 applications. On the other hand, as a system designed to transport applications built on top of X11, NX 3 shares with X11 most of its limits and most of its technical deficiencies. At least all the technical deficiencies that we couldn’t work around because we had to respect the X11 protocol semantic and follow the way X11 applications throw the X11 protocol at us. So we started afresh and designed NX 4 to be a remote display system with none of these limits and technical deficiencies. We did a good job, I think, if our only competitor seems to be our own “old version”.
We tried to keep a single code base and move ALL users to the new system because keeping 2 completely different display systems in place is expensive, but since NX 3 was so good, we couldn’t make everybody happy. Some noticed a small performance decrease when running the same applications (and this was an outstanding achievement), some were extremely happy to see that now they could do things that they were never able to do with NX 3, and finally some others found the new system inferior to the old for the use cases they were interested in, that’s all that counts for them (then there were those who didn’t like the fact some things that were free went into a pay-for version, but that’s a different story). I believe in a couple of years nobody will look back to NX 3 with nostalgia, but when you have a system that works well and make people happy, why throwing the baby out with the bathwater? So we introduced this “lightweight” mode. The lightweight mode is available in the Linux Workstation and all products providing Linux virtual desktops (so no lightweight mode for the free Linux version that doesn’t have virtual desktops). It works in the same way as NX 3, that is by using the glorious X11 protocol. Fonts will never be blurry and the responsiveness will be the same as you were accustomed before, but probably you won’t be able to watch Netflix or YouTube, do videoconferencing, play a game or connect 10 users at the same desktop. But if you don’t care watching Netflix, doing videoconferencing or play a game on the machine you use at work, lightweight NX 4 sessions are what you are looking for.