This seems to be a Starhub Android 2.1 & 2.2 problem. I am using a Motorola Milestone XT720 which is on Android 2.1. I noticed that the connection is very slow on my phone when I got it and that some website which download ok on WIFI just cannot be loaded on 3G or HSPA.
After running between Starhub and Motorola service centers, I found out the following:-
1) Our Starhub SIM works smoothly and very snappy on iPhones and Android 1.5 Motorola phone. I am talking about same location. That's why I believe the problem cannot be location base.
2) Both M1 & Singtel SIM cards works perfectly and very snappy on my Milestone XT720.
3) I just tried my Starhub SIM on my friend's HTC Desire Z. Same problem. Slow like hell.
After bugging them (both Starhub & Motorola) for a while, they gave me a solution. Not perfect but it vastly improves my connection. Here are the steps, give it a try and please share with me your experience.
1) Click on menu button->settings->Wireless & network->Mobile network-> Access Point Names
2) You would probably see "Gee 3G/GPRS".
3) Click on it and clear out the "Proxy" & "Port". Yes. Just delete the contents of these fields.
4) Power off your phone
5) Remove the battery and SIM card and wait for 2 minutes before putting them back and restart your phone. This step seems crucial as I have tried step 1 to 4 without it and it does not work as well.