I have written a review on MY experience using 2 different 3G speed increase hacks. If you don't want to read all of this, feel free to read the Requirements and instillation. If it does not work, no worries, it is easily removed.
As usual I take no responsibility for any damage you may do to your phone. Nor do I promise you this will actually work for you!
Root - I believe this can actually be done with out root, but I dont feel like digging up the instructions on how to make the system writable, pull the build.prop file, how to edit it yourself, push it back and then unmounted the system as writable. However if some one does feel like it, I will be glad to link to the instructions here.
I have found an alternate hack besides NirtiScript. In my experience, NitriScript was not kind to my average speed. My speed test graphs showed very pronounced spikes. In other words my speed was not very consistent at all. I am not bashing the developer of the NitriScript. I appreciate his efforts, but his script was also written in away that is rather secretive. On Monday of this week, I sent him a PM asking him to reveal the source code of his script. At this point in time he has not been online since he posted the script so he has not replied to my request. I like the fact the method I am posting here is completely "open source" so to speak and I did see some increase in speed. Maybe it is purely coincidence, but with the open source nature of this hack, if it doesn't work, it is easily remove.
This method is universal and can be used on any android phone on any network, but may take some tweaking. I have used the hack as is not tweaking it at all
Short Version - Wile I appreciate the effort of the developer of the NirtiScript, I felt the build.prop hack I am linking to below was the better method of the two. I saw higher speeds and generally more reliable speeds.
Detailed Version - If you want the full details of my findings: here
For those who feel comfortable doing this, you can simply copy and paste this in to your build.prop. If you already feel comfortable doing this, then I doubt I need to tell you how.
If you want a zip you can flash, it can be obtained in the thread linked to below. You need to do the following.
boot into Clockworkmod Recovery using Droid 2 Bootstrapper
make nandroid backup if you like.
select install zip from sd card.
[Mod] Improved 3G/Edge Speeds