Got my Gx30 last month and to start with i did'nt like it at all, In fact i went to the Vodaphone shop to see about swopping it for a Nokia, But the bloke in the shop surgested i give it a week just to see, And i'm glad i did. Its a cracking phone when you get used to it, Picture quality's good, Sound's are some of the best you'll hear, But the best thing is the SD card, Which means you can take the card out off your phone, Stick it in to your computer (using a card reader, about a tenner on the high st.) and put in your own wallpaper, music and even ringtones. Its so good there's already two wed sites dedicated to the Gx30. Gx30.com & Gx30.co.uk

I hope this helps!!
PS. I dont know anything about the Gx20.