I've been using the DR-44WL for the last year, it has many of the same issues as the 70D. The 44WL is just as picky about what cards you feed it- write errors and glitchy recordings. I've been using an approved 32G card in the 44WL with no problems. The same card appears on the 70D list so I moved it from the 44WL to the 70D, performed the Erase Format and let it write until it was full-- 24/96, 4 channels @P48 with no discrepancies noted. I always backed-up the 44WL with an M10 and will likely do the same with the 70D, at least until my confidence is higher.
Still saving for an F8 though...
I ran an M10 as backup to my VMS>70d, but stopped doing so after a YEAR of never needing to use then M10 source
So I sold my last M10 and bought a 2nd 70d. No issues at all with either of my 70d's, and I've owned the one for over 1.5 years
Plus they have XLR INS w Phantom Power and the M10 doesn't! I do miss the super small size of the M10, but I only record openly these days, so the bigger size of the 70d isn't an issue for me at all! You'll hopefully relax a little like I did and see that you don't need the M10 as a backup since v1.13/1.14 FW came out, and you have an "Approved" SD Card
I do love the F8's much nicer screen and layout and build, but IMO it doesn't sound any better than the 70d/701d! As always, YMMV! That said, I still think the F8 has HQ preamps and sounds great and is a great deck, especially for having 8 x XLR INS w Phantom, the ability to do a "Safety Track" like the Tascam's do, where it writes another file at a -db level of your choice to avoid clipping, and all of that plus a kickass screen with many options for UNDER $1k, so best of luck saving up for it
I'm sure you'll be very happy with it! Just don't forget to run a backup SD card with your F8, since Ive heard of other tapers having issues where it had a write error to the 1st/Main SD card, but wrote fine to the backup SD card? Maybe they fixed it or that's fixable through a FW update tho? Still a badass deck overall! If I didn't need [2] separate decks, Id probably have an F8 right now, instead of [2] 70D's