the network switch is yet to happen, so I've not been able to use it yet (keep checking, waiting for O2 to drop off!). I don't really use a phone much as I'm at a desk for 10hrs a day, so the low tariff really suits me.
I'll do a bit of a mini review once I've had it a while. From a side-by-side comparison in the shop, the S screen looks a little less vivid than the X, but I found (switching between the same websites) that the S moves a little faster, and oddly the youtube clip I randomly selected looked a bit sharper on the S.
That said, it's VERY big (I may grow to hate it for that). The X is even bigger tho! These phones are £400ish Sim Free, and this one (unlocked) is costing me £384, including the minutes/unlimited data for 2 years, so it's really hard to beat - that's 1/2 the price of an iPhone 4S...
For anyone interested in the deal - it's with carphone warehouse (deal of the week, expires tomorrow).