I'm running Sprint on my stock 6.1 TP2 here in Las Vegas and my speeds are noticeably slower than OP's.
Before installing SH4Ys Raphael Net Speed Boost.CAB I was getting between 100kb/s - 400kb/s on Opera 10, which is totally pathetic.
Afterwards I'm getting in between 200kb/s - 700 kb/s. Not sure if this is just a hiccup or anything but there was an improvement. At what cost, I don't know.
Opera 10 Final Before:
Opera 10 Final After:
And for sh!ts and giggles;
Opera Mini 5 beta Before:
Opera Mini 5 beta After:
Shouldn't Mini be irrelevant seeing as it's rendered server side? Also, the numbers aren't that big of a difference on Mini, so it just could be that I ended up getting it a little higher as a fluke. Correct me if I'm wrong please.
I ran three tests on each go (before/after - Mini/Mobile) and these are the highest numbers on each. (I'm too lazy to do an average)