I agree entirely. The trouble with PDFs is that I have to print them out (not having a laptop, nor any desire to use one at the gaming table really), which is fine for an adventure or supplement of perhaps 32 or 48 pages but hardly cost-effective for anything beyond that.
However, I sometimes find it handy to be able to print sections of larger books to use as player handouts or reference materials, so having books available in both formats, perhaps with very short or niche products only in PDF, would be the ideal for me.