I've been riding a "fixed-gear" bike for more than five months now – and can't imagine going back to a "freewheel".
For those of you who are not familiar with the jargon, a fixed-gear bike is one with just one gear where the pedals keep turning as long as the bike is moving. That means that you can't just stop turning your legs when you pick up speed on a hill. Your legs have got to start revolving faster too.
Like most single-speed bikes, mine has a reversible back wheel, which allows you to choose between riding fixed or freewheel – and until last October, I'd always gone for the latter, whereby I didn't have to pedal the whole time. Then, after repairing a puncture in a hurry, I accidentally put the back wheel on the wrong way round – and decided that maybe this was a sign that it was time for me to give fixed riding a go.
Although it took me a few days to get comfortable (training my brain to keep my legs turning even while travelling over speed bumps or around corners), I soon adjusted, and then became addicted.
The thing is, if I was asked to defend my choice, I'd have to concede that the only real reason I won't switch back is that I feel just a little bit "cooler" now that I'm part of a growing London cult.
I can make a strong case for using a single-speed bike if you commute to work. With no gears, they're much lighter and simpler machines, and cost much less to service and keep in good nick. The extra effort that you have to put in on the hills – or when you start off at a traffic light – is also great if you want to get in shape.
But as for removing your ability to freewheel – I can't think of any good reasons, other than it earns you a little extra kudos on the road. In fact, if I'm totally honest, I'd say it's probably more dangerous to ride fixed than freewheel as there's a greater risk of coming off on corners (by catching a pedal on the ground), and you can be somewhat less manoeuvrable in tight spaces. If your chain jams or snaps, you're also more likely to go flying on a fixed.
Nevertheless, there is something strangely addictive about it. And if you're a confident and able cyclist, I'd recommend giving it a go. If you're not yet convinced, take a look at sheldonbrown.com, which includes a passionate defence of fixed-gear riding.