I am recently having an issue where tethering my PC (Arch Linux) to my Galaxy S2 has a very strange result.
While tethered, web surfing on my PC is painfully slow - not because of slow download speeds, but because the latency between fetching the page and the associated images/scripts can be minutes. I have verified this using Chromium's developer toolbox. This has the effect that badly designed websites don't show up for ages due to the browser waiting to download scripts (or time out) before rendering the full page.
Downloading large files, I can average >100KiB/s, so that is not the issue.
If I connect through WiFi tethering, then both the PC and my Asus Transformer tablet have the same issue, so it would appear to be an issue with the phone. Also, browsing on the phone is as I would expect, quite reasonable given that I don't have full signal, but not unusable as the tethered devices are.
I have also tried running a proxy on the phone to see if it was Three slowing me down (some of them apparently use the TTL count to see if you're tethering), but no luck.
This only started recently, and I didn't change anything on my phone at the time, though I have since gone from CM9 to CM10 to see if that would help. I may have changed something on the PC, though it was working fine on the WiFi broadband until that died (another story, hence why I'm tethering)
Hopefully someone can help me, I have a reasonable level of skill on Linux, so can help in possibly obscure ways if required. Just not sure where to start looking - the fact that both tethered devices have a similar problem points to it being the phone, but not sure how to diagnose what might be causing it.
Hopefully that's enough info, but if you need more just ask :)