Forget wp7.5 and get wp8. Its great at what it does. Has less apps than android/iOS but its an excellent smartphone OS.Visually striking, smooth, easy to use, strong ecosystem in Microsoft services (windows 8, xbox, skydrive, outlook) and good support of gmail.
I had a WP7 device and now have a WP8 device. I would skip the 7.5 devices and get a WP8. If you aren't in a rush wait a couple of months to see if some of the kinks have been worked out of these new phones. Otherwise they are nice to use.