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soens
A bit expensive ($149, $249, or $349) if you just want patch name capability, which Sonar already does.
I know it does a lot more but I already have a FREE patch/sequence editor for my rig.
True, but Sonar is a dead-end now without further support, and the majority of serious users are looking into DAW alternatives that do not have the same capabilities. This is an good alternative if you must have external patch support.
Having a patch editor is also a big plus for older eyes that tire of squinting at at tiny screens. 
OK as a Midi Quest I would say that if you only use it for Instrument Definitions you've missed the point.
It can help you manage Instrument Definitions and the implementation in Sonar makes that a lot easier than Cubase a feature that I will miss.
Where Midi Quest comes into its own, assuming that you have enough supported hardware devices to justify the cost, that of course could be 1, is the ability to manage your MIDI devices sat by your computer. As already pointed out sound editing is made really easy and the ability to undo a change or save a version of the sound before you make another edit really help.
Another feature already mentioned is the ability to save the current setup quickly then restore it at a future date. You could do this on a per song basis or use a timeline approach. Another trick that I liked with Sonar was copying SYSEX data from MIDI Quest and pasting it into the SYSEX View which is just so much easier that creating Dump Request Macros.
You can create libraries of sounds by device and these are great if you remember to tag the individual sounds otherwise you can end up looking for a needle in a haystack. If you have previously bought sound banks for your Synth you can normally open and manage these in their original format which is useful if you remember that the sound you want came with "that set".
Most of the Editors are pretty well laid out. There will always be some compromises because its Universal rather than product specific. There are also a few different styles so sometimes different elements are displayed alongside each other while for other Synths the Elements will be on different pages. I have learnt that when I can't see what I want there will be an option on the screen that will reveal it.
There are various randomisers and morphing features for times when you run out of ideas and are looking for some inspiration. You can also search for "similar" sounds which is useful but you have to remember that because it is basically a HEX data comparison you get some weird results as well as useful ones especially for S&S type modules. Note that there are also ways to limit/control these features.
What I find really great about it is that it enables you to focus on the synthesis process rather than the specific devices architecture. Want to alter an envelope? It will be there on the screen in a graphic form with editing options. Want to alter the texture of a sound that combines multiple samples? You can quickly isolate the individual samples to hear what their contribution is and decide which one, or ones, to change. Of course you can do this through the hardware but what Midi Quest does is let you focus on the what instead of the how.
They also made a point of collecting as many Public Domain sounds as they could find for the supported devices and creating their own online libraries that you can access via the web (assuming that you have not decided to keep your system offline).