Large files are a weakness on the Librie. I hope they fixed this on the Reader, along with a whole shopping list of other BBeB issues...
For example, I noticed on the book store last night that many titles were noticeably bloated compared to other ebook formats.
BBeB you usually get sentence/format unit level compression.
PDF you usually get page compression.
LIT you get whole book compression.
Don't worry, I have many 150MB to 300MB PDF files I'll run on the Reader the day I get it. Euphoria won't keep me from reporting back.