I’ve got a 550 but I’d like a 660. Are they any good?
why do you want to upgrade? aside from the smaller screen, what useful features does the 660 have? i ask as i got my dad a 660 for xmas, and if you hunt around, they can be had for the same price as the 550.
the only differences i could find was the fancy 3D building thing, and how it tells you which lane to be in…
I just fancied one.
haha, fair enough. the 660 is certainly good, but its essentially the same as the 550 just in a different set of clothes and has a bigger screen 
There’s a thread covering this on http://www.zumoforums.com/
You’ll need to be registered to read the thread but it basically says if you have a 550 and it’s not broken, don’t replace it.
Direct link to thread -> http://www.zumoforums.com/index.php?topic=10983.msg86400
I have 550 and 660 and much prefer the 660 
I decided to get one in the end. I think it’s brilliant.
Selling the old one ? 
I sold my old one, sorry. It was advertised on the site for about 5 minutes.
I recon I’m gonna get one of these in the next few months. How much can a used one be gotten for?
660’s hold their value really well, 550’s can be had from £250-£300 ish. you may aswell buy a brand new one imo
660’s are the latest so will hold their price lol The 550’s were only £350ish new but doubled in price last year.
I’ve got both, the 660 has alot better features and is easier to touch/read and dabble with, I use both (and get confused) my 550 I use on the other bikes to save changing all the cables and cradles.