How practical is a Tri specific bike?

This winter (2010) I decided that I wanted a more road biased bike for competing on.  My biggest concern was that my training is my commute to work, so I was concerned that a triathlon specific bike may be unsuitable for commuting.  I checked a few websites, but the standard view was that I should go for a road bike.

I decided that I'd go for it, and build a tri specific bike.  I based it around the Planet X Stealth Pro Carbon frame-set.

Is it any good for commuting? - Although it took a few rides to get used to something other than a XC bike, the bike works well for commuting.  I carry my work clothes, shower gear, bike repair kit and a heavy duty lock in my rucksack - and I've really enjoyed the experience.

So if like me you want a bike for Triathlons, but will use it as a daily ride - you should still consider a tri specific bike.

Are there any downsides? - these are below, but nothing that can't be dealt with:

• Brakes... compared to the hydraulic disc brakes that I'm used to, road bike brakes aren't that good. This isn't a tri-bike issue, but it feels wrong that I can be doing 40mph, and then struggle to stop when the lights change.
• Lights... I haven't yet found lights that will fit on the bike, due to the shape of the frame.  However, there is a guy at work who has some very tiny lights... I don't know what they are yet, but they look like a good option.
• Finally, I haven't got over the new bike thing yet - so I'm very cautious about where I leave it.  At work I have access to the secure-ish car park... I haven't risked leaving it at the pool yet!

Bikes

One of my concerns when training for my first triathlon was would my bike be suitable... I was riding a slightly modified Charge Duster, which after a year of commuting now had semi-slick tyres, higher gear ratio (front large cog up from 42T to 48T) and bar ends to help climbing.

I needn't have worried... my first Tri was a sprint, and there were around 10 other mountain bikes... and half of them still had full off road tyres.  This first triathlon showed me that it really didn't matter what bike you road.

For my standard distance race, there were only two other mountain bikes (that I noticed), however I overtook a lot of road bikes during the event.  If there is a lesson, it's that the training is more important than the bike