I have 4 Par 56, 300W wide beam pre wired onto a lightweight aluminum bar and aluminum stand. If anyone is thinking of getting these types of effect these are my comments:

Plus Ponts.
They are very good a filling the dance floor with light, especially in larger venues.
Great when the band say, "cheers mate can you point them on us!"
Very Lightweight
Low initial cost
Quick to set up, especially if pre-wired
Colour filters can be quickly changed
Look atmospheric with smoke or haze
Choice of narrow, medium and wide beam bulbs.

Negative Points.
No beam control
Take up quite a bit of space
With 4 lamps on, that is 1.2kW, just watch total power loading
Bulbs expensive, and when fail can knock out triacs on controllers

Par56 lightweight!! I had 2 setsof eight & when I weighed them they were 42lb in total. Every gig a lamp or transformer would blow so I converted them to ECS lampholders with standard 60w bulbs. The 2 full sets now weigh 11lb and I haven't had a bulb blow in 2 years. The inductance load of them also means that you cannot use as many per channel as with normal spots. Add to this (as you point out) the cost of each lamp, which also has a low usage life, and it is an expensive (& heavy) way to produce an effect.
Sorry but for me it's a
Pauls

Par 56 are mains operated lights, approx 7" in dia??? They are the shorted version of the Par 64, the classic lamp for rock concerts especially in 1000W narrow beam guise!

I use them nearly every weekend and I've had one bulb go in 2 years!

Pauls, are you referring to Par 36 lamps, these have a 6V 30W narrow beam sealed bulb and an integral transformer? I have eight Par 36and have used them for nearly ten years without a fuse or transformer failure. And if my memory is good only had to replace a couple of bulbs. Par 36 look great with smoke!
As you say they are quite heavy!

What controller did you use?

Sorry Cheezy
I got my 3s & 5s mixed up (new motto - Please help me to keep my mouth shut until I know what I'm talking about )
I was using the PAR36's with a Ryger 4 channel light chaser.
PaulS

its easier to buy colourchangers, you can get them for around £350 for 4 of them. and they are better than par cans and a lot less hassle!

I started out with these type of lamps eons ago....Only ever had to change 3 in 2 years, which isn't bad compared to todays 'bulb' lighting.
Many duo's and bands still use them, and look good for general atmosphere fx.
They're not that bad!

I got rid of mine as I really bent and bashed them up!!!!

I use 4 par56 cans which I have attached on the top of a tbar, with the 'intelligent' lighting beneath them. I think they are great for the right time in an evening, eg the bride and grooms first dance, the last few of the evening, etc. The colour flood works well with the slower songs, especially when guests are taking photo's during the first dance.

Apart from these two situations though I don't use them, many of the bands I work with have now chosen a couple of colour changes, those NJD ones for example.

Ive seen many disco's in this area leave them on all night which I don't think looks particularly great but at the right time they still have their place next to the most modern lighting effects.

Steve