I have noticed a bit of lag once for a few minutes in ordinary game-play, but that is only after being on Crystal Blue for many hours, and my PC is not high-end at all. ( 1.67GHz Athlon XP, 512 MB RAM, Geforce4MX ).
Looking down at Hydlaa from the top of the big tower and pivoting your view around, yeah that will lag things a bit, but you expect that when you are redrawing and recalculating lighting and shading of the dozens of buildings in view at any one time. The complexity of graphics operations does not come close though to modern comercial FPS\'s like Quake and Half-life - if your computer is sufficient to play these at acceptible speed & resolution then it should handle CB well, even though the CrystalSpace engine is certainly not as optimised for rendering as the commercial game engines are.
I suspect the majority of the lag is network ( throughput or latency ) related, and not something you really have any control over from your desktop, regardless of what hardware you have available, assuming you meet a reasonable minimum configuration.
Congestion upstream at your ISP is probably a cause, or downloading in the background while Planeshift is active. From memory the client - server communication uses UDP packets, which is less forgiving of lost packets than TCP, but is suited for real-time data, like your characters (x,y,z) position, velocity and acceleration, and pending actions (attack, chat, and so on ).
The planeshift server ( laanx.fragnetics.com ) itself does not appear to be too heavily loaded in a general sense, see the stats links on the left pane of the main page at
http://laanx.fragnetics.com/.
Freeing up as much RAM as possible before launching Planeshift ( by shutting down other applications and systray applets ), and keeping your harddisk defragmented ( planeshift opens up .zip data files as its running, this is disk-access intensive, especially when in complex sectors adjacent to many others, like Hydlaa ) is probably the best thing you can do to keep lag down without investing in additional hardware or higher speed internet connections.