Ran across this older thread and thought I'd add a couple of comments.
When the inevitable thread about "what are the differences between the 2000 series and the 1000 series" comes up it would seem that the ability to make fine (vs. coarse) adjustments on the horizontal scale should be on the list.
To expand our database: The Rigol DS4000 series also has the variable timebase feature, implemented as the "coarse vs. fine" as described.
It's not a huge feature but apparently some people use it or would like it....
It's an important feature for me, if only for the following reason. I like to characterize my firmware so that I understand what percentage of CPU time various modules are consuming. When you're considering choices between integer and floating point math, etc. the amount of CPU consumption can be critical. One way to do this is to set an I/O pin when you enter the code in question and clear that pin when you exit. The result is a pulse whose duration indicates time spent in the code, and whose duty cycle indicates the percentage of CPU consumed by that code. Modern DSO's can automatically calculate and display those values.
Code taking different branches upon different invokations appears as jitter. Thus it's nice to average these measurements across multiple pulses. And here's where the variable timebase comes in. It's very unlikely that the period of that waveform will be a convenient multiple of the 1-2-5 timebase sequence. But if you don't correct for that, then the DSO's duty cycle measurement can be off because the DSO calculates those values based on the display. So you use the variable timebase feature to dial in the display such that it's showing an integer multiple of the debug waveform (generally, the left and right edges of the display are both on a rising edge of the signal). Now the screen is displaying an integer number of invokations of the code in question, and the DSO's resulting calculation of duty cycle reflects the percentage of CPU time that is spent in that code.
Doesn't everyone develop and debug firmware with an oscilloscope?