Currently using Google Drive and Google Sync. 1TB for about £6 a month. It just....works. I drop photos on any of my PCs (home, work and laptop) and it ends up synced everywhere. I've not noticed any upload speed issues either- my initial 200Gb of photos took an evening. I also keep all my music there, basically anything I need accessible.
Not everyone will like this, but Google+ also does some interesting things with photos, it chooses similar ones to combine into little animations, and organises albums by time and location, and does some half decent automatic post processing too. I don't publish any of it, but it'd be neat if you wanted to.
Having said all that, as an Amazon Prime member, it'd be interesting if they offer the unlimited photos to the UK, in which case I'll bung all my mobile and non-RAW photos there instead.