I moved to a Linux (Ubuntu) operating system a couple years ago and tried Gramps last November. My view as follows:
Transferring my rather large data file (23,000+ names) using Gedcom was relatively easy and I could even transfer my photographs into Gramps with little difficulty.
Gramps, however, is without a doubt the strangest genealogy software I've ever used. Nothing is intuitive and moving through the files feels oddly convoluted. I spent a month trying to acclimate myself and, at the end of that month, I was no more comfortable with it than when I installed it.
In frustration I finally dumped Gramps and went back to Legacy using Virtualbox. I'm still a Linux user but I boot into a Windows XP virtual machine to do Legacy.
The bottom line is, for some, Gramps might work fine but it in no way compares with most of the Windows application. Try it and I think your experience will be the same as mine.