Yep, hivi doesn't just make you look a wally, it makes you feel one too.
Great thing is I can't see myself when I'm on the bike, so I really don't care.
The great thing about looking a wally is that you stand out and people do actually see you. They might think "what a prat" but they've seen you.
When I'm riding outside of rush hour, I don't bother with it. When I'm commuting and therefore doing a lot more "inventive" riding (over taking, filtering, etc) outside of the normal flow and position of traffic then I feel a hivi is hugely advantageous. Far more people get out of your way and this is easily measured by the amount of "thanks!" waves I give as I go past. Yeah some people see you and block you off - they're called f**kbends and should be treated as such.
If you're riding outside rush hour then the amount of filtering and over taking you'll do is limited and on top of that you should have the mad defensive riding skillz (innit, because I is down with the kids) to keep you safe. Everyone who is sat at a junction hasn't seen you - looking at their face might work in a car but for a bike, you look at their wheels and establish on your approach if they're on the handbrake or the clutch. If their wheels move even an inch, then beep them. They might get irritated because they wern't planning on pulling out but if they've got half a brain cell they will remember that half of it is conveying what you're doing to other people so they feel safe and can accurately plan what they're doing without the wild card of the person who insists on rolling forward and back on the clutch at a junction. 3/4 of accidents where a driver claims not to have seen a rider happen at junctions. I have personal experience showing that in some cases they're just cocks (he pulls out, I beep, they stop, I carry on and they pull out anyway. He floors it away and years later I'm still on pain killers. Wanker).
What's interesting is that there are so many people who will think this kind of analysis of the nuances of using the roads is pathetic but then they're obviously blinded to the risks by their airbags and (ME)NCAP safety ratings. RTAs count for almost half of all accidental death in Britain and the largest single cause of death for young adults.
Someone asked for stats - I can't remember exact figures for all of these:
Bikes = 1% of traffic, 20% of fatalities
Majority (3/4) of accidents in urban areas
Majority (just over 50%) of fatalities in rural areas
Majority of accidents and KSI accidents on over 500cc machines
Peak age being killed on a bike (surely off a bike?) is 17
20 year olds have 3x the accident risk as 30 year olds
The average rider will have more than 8 accidents if they start at 17 by the age of 35
In an accident a biker is 35x more likely to be killed or seriously injured.
8x more likely to be involved in an accident resulting in injury.
Studies have shown that a hivi and 55W halogen bulb make you more obvious.
You can see why the Police are targeting bikers and studies have shown that during the day about 1/3rd of accidents involving another vehicle were caused by not being seen. At night this rises to almost half. Remember that at night, you're one little light amongst many. You're riding along working on the same principle as disruptive pattern material used by the Army in their camo and you expect to be seen? Those other lights will reflect off a hivi, making you stand out more.