I just bought one a few days ago, handset only because I didn't want a contract. The price was a fraction of the iphone so not really a fair comparison but it stacks up pretty well. I have used an ipod touch for a few years now so was worried that I wouldn't like the 5800. The ipod is now relagated to car duties.
It's definitely less slick than an ipod but after two days I really like it, the stylus isn't necessary but sometimes its easier, opera 10 is fantastic, sports tracker is great and one of the main reasons I bought it, GPS locks on quickly, no slower than the garmin edge I used to have. Just waiting on the windscreen mount to use it while driving. Early days but I'm really happy with it.