If I Image using Macrium Reflect, my 60GB takes almost exactly 60 mins to ext HDD via USB2. While Easeus Todo takes 120 mins for the same. (max compression on both)
I seem to remember W7 Image in Backup&Restore Center was between the two. (no compression settings allowed)
I stopped using it in the end and always found problems with W7 Backup (not Image) as well.