Here's what I have to say about it so far:
The battery can easily go for one week on very low usage.
My definition of low usage: Phone is turned off from 11pm to 9-10am the next day, with minimal calls, SMSes and web browsing.
No problems with calls and messaging.
The GPS has proven itself when I went to the Bug-O-Rama last week, however it tends to lose signal when underneath an overhead highway or if the road is lined with trees. You can have it guide you based on the shortest route (aka default), the route with least traffic (data charges apply) or based on checkpoints/landmarks set by yourself. Voice guidance is clear, although I'll need a contraption to hold it to look at the screen while driving.
Browsing with Opera is good.
There was an interesting story with the video recording however. After my day at Sepang (Which happened to be soon after I got the C5), recorded videos were terribly choppy and took ages to save. A minute's worth of video took something like 10-20 seconds to save. I was about to take it to a Nokia Center, either in SS15 [not sure if it still exists] or Amcorp Mall near my college. But then one day I got a notification to update the phone software for "performance and usability". I thought, what the heck, go ahead lah.
Once the update was done I had no more issues with the video recording and saving videos is much much faster (less than 3 seconds to save a 1 minute video). I might put up a before/after comparison if the mood comes.
Legibility in bright sunlight is very good, only if the screen brightness is turned up to maximum. My regular screen brightness of about 40% makes it almost impossible to see the screen.
One, real (but minor) problem though...
The center navigation key is starting to flake off its paint. Quite a letdown I must say...
But overall, still a good performing phone.