I also have one,
Like Kowalski said camera is not very good, especially under low light conditions.
Some of the older 5800XM s are said to have an ear piece problem, where the ear piece stops working after few months. But Nokia has fixed this in January therefore, phones manufactured after Jan should be fine. However , there is no sure way to check the manufactured date of a phone, instead you can check the firmware version; if it is v21 or later then most likely the phone is manufactured after Jan (assuming the shop didn’t update the firmware, which normally they don’t). but then, again this earpiece problem is easy to fix, so its not something to worry too much.
Again as Kowalski said, touch screen is not as responsive as in iPhones, because Nokia uses a different touch screen technology called capacitive where as iPhone has a resistive touch screen. Despite the somewhat less responsiveness, capacitive touch screens are better because you can use it with a stylus or with just about any hard object, On the other hand you have to use bare fingers (no styluses or not even fingers when wearing gloves) with an iPhone. But overall, its responsive enough.
My personal opinion :
I like it a lot, IMO you can’t get a comparable touch phone with this feature set (Smartphone, Wi-Fi, GPS, Screen size, QWERTY Keyboard) in the same price range. Battery life is also pretty good, especially when listening to music. It is rated for 35hrs for Music (since it has a dedicated audio chip). And I love the onscreen QWERTY Keyboard, its so much easier to type. A hardware KB like in N97 would’ve been great, but touch QWERTY is the next best thing..
If camera is very important and don’t mind the lack of a touch screen then you might want to consider something like N85 (which IMO is slightly more expensive), Other more cheaper 5MP camera phone alternatives with more or less the same feature set without a touch screen are: N79, N95, N82, 6220 Classic.