I didn't really start gaming until after digest size books were already phased out. My first roleplaying games were the Moldvay "Basic" and "Expert" sets and "Marvel Super Heroes". The majority of books I've owned have been standard letter sized, and I've pretty much gotten used to this.
The first digest-sized book I owned was "Big Eyes, Small Mouth 2e". Talk about something completely different from the old school games. I then picked up some of the small press Lulu stuff like "Jaws of the Six Serpents" and "A Dirty World", which are also digest books.
I kind of like digest books. They're compact and don't take up too much space. My biggest issue with them is the small print that is commonly required by games, as well as the limited space for art. It's a trade-off. BESM was one of the few digest books that has very legible fonts and great art, but it was also over 300 pages long.
Certain games, especially those geared towards old school DnD, actually have a bit of charm when presented in the digest format. It tweaks the nostalgia nerve for the grognards, and makes the books stand out from the standard rpg fare.
In the end, by going digest size, especially for something like White Box, the digest size gives them their own identity. As long as the font remains readable, and art isn't relegated to just a few pieces per book, I will happily support the digest format. But if fonts shrink too much, and art becomes really rare, I will urge producers to go back to Letter size format.