When I found out that Goodreader crashes or doesn't even open powerpoint files larger than 30mb, i decided to buy Document to Go. After reading many reviews it seemed to be the logical choice. Unfortunately pptx files are extremely slow. If d2g opens them, there is a lag up to two minutes per slide. Simply amazing. Fortunately, my samsung galaxy s2 always rescues the overpriced ipad. Doesn't matter how large the pptx file is, my android phone is able to download the file from anywhere (internet or cloud), stores it on a mutual location which can be accessed by any app and opens the pptx file in its stock app without any hiccup. Apple's stock viewer doesn' open large ppt files either from safari or mail.