I was in the market for an oscilloscope, but I didn't want to spend much. I found out about Rigol and their line of $300-400 scopes, and was getting ready to buy one. Then I found a post on how to make your DS1052E, which costs about $400 into a DS1102E, which costs about $700 with a simple firmware modification! I bought the scope right after, and I received it in the mail today. It's pretty nice by default, but doubling the bandwidth is always a plus.
The DS1052E has a 50Mhz maximum frequency, but it has exactly the same hardware (as far as the reverse-engineering folks can tell) as the DS1102E, which has a 100Mhz maximum. This guide will show you how to make the switch very easily using Linux. You can do it in Windows too, but it's a bit more involved, and Linux makes it really really easy.
I've attached the Rigol user guide for both units, in case you don't have one.
WARNING: It's entirely likely that this completely voids your warranty. Make sure you know what you're doing - you can brick your scope if you screw anything up.
Step 1: Spec Comparison
Here are the specs of the 2 scope models. Our test to see if we've succeeded is by looking at the Time Base Range minimum setting - the DS1052E has a 5ns/div setting, where the DS1102E has a 2ns/div setting - a much more accurate view for sure!
Step 2: Get Linux Running
The first step is to get Linux going if you don't already have it. I use Ubuntu 10.10 as my desktop OS, so I was able to skip this step. If you don't want to continue running Linux, and just want to get this scope flashed, you can download the Ubuntu LiveCD, burn it, and boot from it.