This is my first smartphone so I don't have much to compare it to, but I just ran a bunch of speed tests under a couple different circumstances to test the 3G speed of my Optimus S (stock phone).
Let me preface this by saying that my apartment is in a really dead zone for coverage. So dead that with my previous phone (which I had until last saturday) I had to go in to either the living room or the den and be near the windows in either of those rooms to have a conversation. Conversations were impossible in other areas of the apartment. (With my new Optimus S I can make calls basically in any room of the apartment except maybe the bathroom, in which the convo cuts in and out. Otherwise the calls are still fine even though I get 0-2 bars in various places in my apartment)
Anyhow, I just happened to receive my Sprint AIRAVE Airvana signal booster today, so I ran some speed tests before installing the signal booster and after (it plugs in to your highspeed internet router and functions as a small standalone cell tower).
Here are the results from the numerous speed tests I did with the Speedtest.net application under various circumstances. Download is listed first, Upload is listed second. All tests were done between 3pm and 4pm central time (traffic is bad outside from people going home early from work because of the holiday, so i assume cell traffic is fairly heavy too?)
In my bedroom (NOT near a window or anything) - 0 bars of service showing and 1x icon showing instead of 3G icon
0.03 Mbps D - 0.00 Mbps U (it was unable to even register an Up speed)
In the den sitting in a chair (approximately 3 feet from window, phone in hands) 1 bar of service and 3G icon showing:
0.20 Mbps - 0.01 Mbps
0.23 Mbps - 0.09 Mbps
0.23 Mbps - 0.02 Mbps
In the den with the phone set directly on the window sill, 2 bars of service and 3G icon
0.32 Mbps - 0.30 Mbps
0.27 Mbps - 0.13 Mbps
In the den with the phone held up to the window glass, 3 bars showing and 3G icon
0.42 Mbps - 0.15 Mbps
0.41 Mbps - 0.22 Mbps
Now I installed the Sprint AIRAVE Airvana and after I was finished I had 6 bars showing and a 3G icon everywhere in my apartment (even in farthest corner from the AIRAVE separated from it by a few walls)
1.46 Mbps - 0.63 Mbps
1.62 Mbps - 0.61 Mbps
1.40 Mbps - 0.43 Mbps
Then I went and ran a couple errands and did some testing along the way out on the road.
0.90 Mbps - 0.67 Mbps (had 4 bars/3G at this point)
0.93 Mbps - 0.67 Mbps (same exact spot sitting at traffic light, 4 bars/3G)
Farther down the road I had 5 bars/3G and got:
1.40 Mbps - 0.82 Mbps
Standing in line at the bank w/ 4 or 5 bars/3G
0.72 Mbps - 0.21 Mbps
Outside the bank in the parking lot w/ 5 bars/3G
1.45 Mbps - 0.30 Mbps
Back in the parking lot of my apartment (back in the dead zone, out of range of the AIRAVE I'm assuming) 3 bars/3G
0.53 Mbps - 0.61 Mbps
Back in my apartment with 6 bars/3G because of the AIRAVE
1.42 Mbps - 0.62 Mbps
1.67 Mbps - 0.63 Mbps
I also ran a couple tests with WiFi enabled, through my ATT Uverse internet service
7.63 Mbps - 1.46 Mbps
8.63 Mbps - 1.46 Mbps
My 12Mbps internet service registers 11.40 Mbps - 1.43 Mbps when tested on the computer (wireless), so the phone is obviously not as fast as a computer even when it's running the test through WiFi.