Used my 405 at Bracknell this weekend in the drizzle. As per normal, it let me down. Bezel sensitivity (which I have tried at all levels) drops when when wet. Auto-scroll sucks also - I dont want to spend 20 seconds looking at my wrist waiting for the correct information - the 305 had all I needed (4 fields) in one glance. Shit I wish I'd bought another one or gone for the 310 instead of falling into the cosmetic 405 trap.
Reading the instructions I have done. Settings I have adjusted. My view remains the same - the 305 was a much better, more reliable bit of kit. If you haven't used one, perhaps you don't know. Maybe I'd be in love with the 405 if I hadn't used better before.
I would say avoid the 405 for various reasons, already stated here. My 305 packed up so I moved to 405. The issues with the bezel can not be understated often giving massive frustration during training and races. It is impacted by wet from sweat or rain. The loss of the 4th data field on the screen is a big issue for me meaning I have to scroll on-the-go to see my heart rate. I also find the start/stop and lap buttons poor quality compared to the 305 front buttons. Last week in Vienna I had to run without the HRM as it dropped connection 1 min before the run started (something that never happened with the 305) and then kept finding multiple signals as I was surrounded. During the confusion (and the bezel taking me to numerous menu items I didn't want - which is quite usual due to its inconsistent sensitivity - you often find you need to unset things that you accidentally set) the 'time' had been replaced by 'clock' so I spent the first few miles trying to change it back.
Lots of people love the 405 but in my experience go for other choices. It looks good and it bluetooth connects to your PC, but apart from that I think my 305 was infinitely better.