I've been playing around with this issue and it seems like this can be fixed by formatting your memory card to exFAT with 64kb cluster size.
Can anyone else play around with this setting and let the rest of us know if this is working for them as well? Thanks!
I'm using a Sandisk Ultra card with 16Gb of storage, Class 10 + UHS 1 like this one:
http://www.amazon.co.uk/SanDisk-micr...pUvbUpU1973683
EDIT 1: I've just format the microSD card back to FAT32 with 8kb clusters, and I can confirm the problem is back, even with memory card completely empty. I've also tested with 16kb clusters and it's still there.
I'll retest this with exFAT with 32kb and 64kb clusters and report back.
EDIT 2: The delay is still there with exFAT with 32kb clusters, it's less than FAT32/8kb but it's still present on an empty card.
EDIT 3: Delay still present with exFAT and 64kb clusters. I can't tell if the delay is longer than with 32kb. Will test further.
EDIT 4: I've tested it further and the delay is smaller in exFAT with 64kb clusters. It's unadvisable to use larger clusters in a 16Gb card, so I can't go any further, but people with 32 and 64 Gb cards may want to try a 128kb cluster size.
P.S.: The feelling that I get is that WP8 shuts down the memory card after a couple of minutes and then when you try to take a photo it has to wait for the card to wake up. Quite stupid really, there should be a memory buffer for this kind of things. :-/
EDIT 5: Seems like there's a side effect to have the SD card in exFAT format... you can't sync anything anymore. You have to manage things by hand.