...so far I absolutely agree:

Adding the VBR-header using vbrfix or mp3tool causes gaps between files, that didn't have gaps between them before.

I will upload several mp3-files onto my empeg (some appear longer, some appear shorter) with manipulated VBR-headers (I changed the frame-count, which is the only thing I was able to find in these headers so far) to see what's gonna happen then.
Too bad my empeg needs to check disc integrity NOW.....

Still I have to say, on my empeg these pauses are USUALLY very short - but from time to time it takes almost a second before music continues...