I checked up on this, and the 5800 has software issues at the start that made 3G spotty for the US but that was last January and solved long time ago. There has been some software updates ever since. Most phones anyway, require updates on the operating system software, no one is perfect right at the start.
The 5800 is one of Nokia's better supported phones, because they have been selling a lot of it anyway, at the ratio of nearly 1 million a month from what I gathered, as Nokia just released their financial results yesterday. Its not up to iPhone in quality, but its also a lot cheaper without a contract and no carrier lock. I tried one out myself, the browsing quality can be described as better than average, not though with iPhone standards, has good music and appears to be an excellent video player.