It would make it a bit less painful to update to latest release if the entire source didn't have to be reinstalled each time. I could see where for major updates reinstalling entirely might be needed. Wouldn't it be possible to just patch a few files with a minor version release?

If you mean uninstall followed by install, no it's never required.
You can install update over existing version.

No, I mean the complete program is more than 60 Mb. I'd guess that the update from build 5625 to 5626 is not 60 Mb worth of changes. I might be more like 2 kb. I'm suggesting that rather than having to download 60 Mb and reinstall the entire program that the program would be able to update itself (if nothing else perhaps just extracting patched files to the applicable directories, etc.).

it's clearer now, but makes very little sense. Indeed, we have say 29 builds for only version 5.6. It means that we need 5601->5602, 5601->5603, 5601->5604..., 5601->5629,
also 5602->5603, 5602->5604...5602->5629,
also 5603->5604, 5603->5605... 5603->5629,
...
5628->5629
and I'm talking about version 5.6 only. What about 4.6->5.0, 4.6->5.2, 4.6->5.5, 4.6->5.6, 5.0->5.2, 5.0->5.5, 5.0->5.6, ... 5.5->5.6 upgrades with all their builds?
Do you really think it worth creating and maintaining all these combinations?
To me it's just nightmare and I don't think you'd like me to do all this work instead of developing the IDE.

On the other hand, it's clear that you see it as OS updates. But PhpED is not operating system and takes only 60MB which realatively small size these days.

I agree, I would not want this to detract from other higher priority items. But to clarify, I was only talking about MINOR updates. 5.6 to 5.6.1 or 5.6.2 (or using "builds"). 5.5->6 would be MAJOR update, as would maybe 5.5 ->5.6.

I guess you're right though, most programs I'm using do require a full reinstall. Maybe I have my brain entrenched in grabbing updates from svn too much ; )

Even in this case, we would have to create more than 400(!) incremental packages for all the builds in version 5.6.