Averaging about 2k ppd right now, although my rig should be worth 4-5k, HD 4870-C2D 84000.
It's simple for me though, when I leave the house for long periods I always shut it off and at night I turn it off, however I have been experimenting with temps and fan speeds and have finally gotten the computer quiet enough that I can sleep with it on (Same room). I got two or three 5k days in so far and hopefully it will continue.
Besides that I have two laptops that don't really fold (One has a serivce console but its only on a few hours a day so it does around 50 ppd...)
The other is a recent 1.83 GHz dual core Turion and it gets close to 500 PPD, I just have to keep folding on it when I'm not using it, (I can't fold while using it because of poor fan design, it can't take 100% without being propped up on its side to get more air)
On the tweaking side, if your running an ATI GPU client, you can set a flush interval value (0-1024) that will reduce GPU overhead 50% so you can get back 200 or so extra ppd for cpu clients.
This is quoted from the ATI Specific Issue's folding forum:
"In your environment, you can set FLUSH_INTERVAL to a value between 2 and 1024. This flag sets the maximum command packet size sent to the GPU. The default in the core is 16 which seems to solve the lag problems for most people, but at some added CPU overhead. People with higher-end boards can manually adjust this value until we deprecate this flag in later cores. The higher the value this flag is, the less driver overhead and lower CPU usage you will have, but there is still CPU optimization work going into later CAL releases and F@H cores. Setting this value to high will cause UI lag and potentially VPU recover and is designed more for advanced users. The lower the value, the smaller the command packet which translates into other graphics apps being able to play nice."
"This is an environment variable you can set via System properties->Advanced->Environment Variables which you can get to via the control panel or described above in P5-133XL's post above. You'll want to set a system variable 'FLUSH_INTERVAL' (without the quotes) and set it to an integer value described above. If you have having lag issues set it to a value less than 16. Note that different size proteins will have a little bit different behavior here. We are working on getting this value set automatically in the future."
All HD 4870 should be fine at 512, mine is running at that and I haven't had a single issue, less powerful graphics cards need a lower setting though. Some people with 4870's can even set 1024 which drops CPU usage 75%, but that starts having errors. Play around and enjoy that little extra PPD!
Also, if you have problems sleeping at night due to noise from an ATI GPU, try reducing the memory clocks, my 4870 is running at 500 MHz Mem, when normal is 950 MHz, but folding only drops around 100-200 ppd. This drops temps about 5 C so you can turn down the fan speed and make it quieter. I don't know how well this works on other cards though, GDDR5 is probably the reason the clocks can be set so low.
Well I hope to get up to 3.5k-4k ppd (My computer is still going to be off for at least a few hours a day) enjoy the little "Tweaks" as well.