Nether - bug testing (lagg/fps issues)

I've been doing some testing on my craftbukkit server today, because nether (for all players) still cause huge FPS drops. (not only on my server). I've done all tests I could think of, if you know anything else I could do, please tell me.

The problem
as many topics describe: entering the nether cause lots and lots of lagg on a craftbukkit server. Huge fps drops (5fps? 4?3?) are common for players like me who don't have a beast-computer.

Server config
- craftbukkit 1.2.5 R3.0
- 0 plugins
- (after testing) nolagg, worldedit, worldguard
- clean 1.2.5 world
- tested with 2 players (one on laptop, one on pretty good computer)
- server runned with 1.25 GB of RAM

Client config
- optifine mod installed with lowest options possible: no fire, no lava, no fancy stuff,..
- no other programs running but minecraft and SSH client for the server (no browser, no teamspeak,...)

The tests
1) Trying to go to the nether with no plugins at all, just like you would normally do in you singleplayer world. the first time entering the nether (creating the world) it takes a while (+-2 minutes) untill the world is loaded and chunks are generated. After that I get random freezes each 5-10 seconds and FPS more than halves

2) Installed the nolagg plugin for craftbukkit 1.2.5. There is no difference at all in comparison without the plugin. Entering the nether is the most laggiest stage, after waiting for +-10 seconds of total freeze I can start to move. When I enter the nether, my friend on his PC also laggs as long as I'm frozen. He also has the same FPS issues, but not as bad as I do on my laptop.

3) installed WE & worldguard, performed the /stoplagg command, seemed that it helped a bit, but not much, after being in the nether for about 3 minutes, the freezes renturn

4) put server difficulty to peacefull so no mobs could spawn, didn't help

5) use the /remove items <rardius> command in the nether trying to remove entities, 0 found in a radius of 10, didn't seem to work so didn't test it any longer

6) downloaded the nether world to my computer and saved it in a clean world for singleplayer, entered it with the same mod config for optifine, and wonder! I had flaweless FPS rates of +-30 (which is good for me =D) all the time, when chunks are generating, the game tends to freeze for a half of a second, but that's my laptop being old.

7) tried to use the mojang server, works almost as good as on singleplayer.

Conclusion
because of the fact that the same world worked on SP/mojang server and not on SMP, it seems to me that this is an SMP related issue. It has been on the forums here before many times, I tried to gather as much information today hoping to get some response. I also must say this issue hasn't been here befor 1.1 came out I believe.
I do want to make a quick comparison: I played WoW (world of warcraft) a while agoon the same laptop I use now to play minecraft on. I could easily get 50 FPS on WoW (which is not a small game) ans play it for hours (I didn't have a life back in those days) without any lagg/freezes/.. the reason? they have a better graphics engine =P that's no blame to anyone, I just wanted to make the comparison for people thinking I might have a crapy laptop. Also, keep in mind minecraft & craftbukkit are written in Java, a wonderfull language but admit: there are a lot of bugs, which wouldn't be here if the game was written in another language.

before we start pro-contra java: it's the only language I program in, it's good but certainly not good for game, MC is the proof. However, I do think things can be improved a lot, that's why I hope some people read this and maybe can help do more tests etc.

greetz
zip

tags
TnT mbaxter EvilSeph Dinnerbone NuclearW