Well the 5800 xpress music beats the iphone in feature except in one place i.e touchscreen.
the touchscreen on the iphone is a capacitative touch whereas on the nokia it is an resistive touch.
the main drawback is that the touchscreen is not quite responsive and u need to apply more pressure than the iphone.
nokia also doesn't have a multi touch interface.
Nokia is lining up a lot of touchscreen phone such as the N97.
They promise a lot more features.
If the phone is absolutely necessary for you then go ahead and buy it without hesitation.
But if you dont mind waiting then wait for 2 months for some good mobiles from nokia.

If cost is not a issue then i would recommend the HTC touch HD, its got a brilliant display and beats all the phones in features.