I have been chatting with Lehto and he apparently runs his at 1100Mhz fixed and noticed that it is much smoother than ever before. (as it doesn't need to scale back down to 250 or 500 speed etc)

So I tried it on my N900 today. Just fixed at 1000Mhz. It's either 0Mhz or 1000Mhz. Using xlv voltage profile with every other supported frequency is in the avoid list. What can I tell ya. It's smoother with less lag than ever before! I'm surprised how responsive my N900 became. I've watched an xvid avi file for like an hour straight and had zero issues still. (my phone never had issues at 1Ghz anyways)

So to those who want that extra responsiveness, try taking out the cpu frequency scaling altogether. (maybe even fixed at 600Mhz or 850Mhz if your phone can't do 1Ghz) I'll bet you will notice it being a little more responsive and lag free. I did. =)

Here is some simple steps I've written up on how to do this:
(I wrote this to cater for beginners also but still with some assumed knowledge)

0. Install an app called "leafpad" from HAM/FAM.
1. Overclock your N900 normally to what you always overclock to.
(will assume that the maximum is set to what you want as fixed)
2. launch xterminal
3. RUN: root
4. RUN: kernel-config min max (where min & max is the desired fixed frequency)
eg. kernel-config limits 1000 1000
4. RUN: kernel-config save my_fixed_oc (or to any other profile name you want)
5. RUN: leafpad /home/user/.kernel/my_fixed_oc
6. From leafpad, we need to edit FREQS line to only show 2 frequencies:
eg. FREQS="0:20,90 1000:60,500 "
(above example means it only allows 0Mhz or 1000Mhz. exact numbers may differ depending on which overclock profile u used. At the end, just ensure you have 2 values in there. 0 and max value you want.)
7. Save and close leafpad.
8. RUN: kernel-config load my_fixed_oc
9. RUN: kernel-config show
(it should show both min and max frequency with same value)
(it should show all other supported frequency in the "avoid frequency" lline)
(it should show only 2 frequencies you set in the "active frequencies" line)
10. You can now use "my_fixed_oc" profile with Queen Beecon Widget etc.

DONE. Now even if you make a phone call etc, it'll still always be locked to max. =)