TJ08-E is fairly big, but I personally really liked it. The drive cage leaves a bit to be desired and it continues Silverstone's weird obsession with screw-heavy PC case build installation. To be honest, mATX is probably more niche than m-ITX. If more motherboards had a slot gap between the two gpus and more mATX cases had five slots, m-ATX would be a lot more popular imo.
TJ08-E is what I'd consider a reasonable size for M-ATX though. Compared to say a 350D it was a baby.
I find it a good size. The Cerberus I've got my email down for though haha. My current rig is in the Ncase M1, ITX, but if I can get something only a little bigger in M-ATX, I may consider that too (or move my brothers computer into it, as he's using my TJ08-E