Quantity over customizability.
Although the RM-VL600 includes more macros than most budget remotes, options for those macros are few. The only way to insert a pause between two commands is, according to the manual, to press the component button again for a 0.4 second delay. This isn't exactly useful in situations where pauses are truly needed, since just 5 seconds worth of delay would require 13 of the 16 available steps.
The inter-command playback timing for macro steps cannot be adjusted from the default setting, which is basically "fast". I timed a 16 step macro with the mandatory 1 device change at roughly 4.5 seconds, while a similar macro with 8 device changes took exactly the same amount of time. These are interesting results compared to the RM-VL710 which clocked in, respectively, at 8 seconds and 6 seconds with the same macros. One other feature that would be nice is the possibility of customizing the 2-second hold time requirement for component select buttons, since the default delay is a little long.
If you don't need all 12 of those macros it's also possible to store a single learned infrared command on each of the macro-capable buttons - useful if all you want is an input command or to turn a particular device on or off. This command will be transmitted instantly each time the button is pressed.
Speaking of powering on devices, the RM-VL600 includes a specialized "power on" function for most Sony equipment that, when activated, will turn on the device when the component selection button is pressed. As mentioned this only works with Sony equipment and can be combined with a Component Select macro on the same button (while learned functions on those keys cannot be combined with anything). There is no matching "power off" feature.
Micro macros - still hanging around!
The RM-VL600's packaging is rather vague on exactly what sort of learning capabilities the remote features. Recent Sony models have advertised that they can learn codes up to 500kHz in frequency and 250-bits in length, far more than average remotes that classically top out at 50kHz and 20 or 30 bits. But despite the absence of technical specifications it would appear that the RM-VL600 does in fact include the same capabilities as previous models - which is great news since that means it's "micro macro" capable!
"Micro macros?" you might say, "Isn't that sort of redundant?"
No doubt this isn't something that you'll see advertised on any of Sony's boxes (although one of their high-end LCD models did turn this into an official capability), but "micro macros" is the process - or some might call art - of capturing more than one command on a single button. You see, most infrared signals require only 8 to 24 bits worth of space, while the RM-VL600 supports codes up to 250-bits long. So, with practice, it's possible to learn four or more commands onto any of the remote's buttons - and those commands don't need to be for the same device or even brand of device. "Micros" are an especially handy way to put favorite channel macros on otherwise unused keys.