How bright is your light? Do you have other lights you can compare it to? Does it have that donut hole in the beam? Sorry for all the questions 
These leads at DX seem like they are pretty good. I have some on the way now. The writing on the wires in the user picture shows 18AWG which would be 18 gauge wire. That should be plenty.
http://www.dealextreme.com/details.dx/sku.33451
I also bought some leads on eBay that look just like those, but even though they are listed as 10 amp leads, they have thick looking leads that are all insulation around very thin wires and can't measure the current either (I stripped the insulation and figure they are about 26 gauge wire). I told the seller about this and they agreed to send me 20 amp leads which they confirmed had much thicker copper inside. I got the 10A leads for $1.28 at auction whereas they sell the 20A leads for $6.99 so that was pretty nice of them (but they got me to change my negative review of them). Once I get some of the new leads I will do the tests again and post the results.
It is BRIGHT. When it stops raining I will do a comparison shots with it up against my R5's. Yes has a hole, but I suspect that can be fixed by removing alot of heat sink goop.(its everywhere emitter too high)
no worries
Ordering a better set leads from dx .
Got the new multimeter leads today and rechecked the draw on my MC-E shows 2.30A now. Its bright I'am happy 
DX doesn't have any more in stock! 
I ordered on 8/16 and the status still shows
| Processing - Awaiting Stock |
I have been waiting for a cpl of drivers since 29/4/10 and I suspect you will get your 501b before I get the drivers..
I was so pleased with my DX 501B MC-E M bin that I bought three more to get the drop-ins to install in Solarforce or 504B bodies.The current drop-in seems to be just as good or the same as the original batch.I don't hear any whine like others have noticed and they don't seem to get any hotter than my DX R2s or my Solarforce R5s.They do have a small dark donut hole,but it is a small drawback considering the huge light output.I use them on bikes in tandem with a Solarforce R5 or R2 which fills any donut hole nicely.So be patient, DX is shipping them out!
Mine too only pulls 1.4 amps so will try the driver upgrade...
New driver fitted but still only getting 1.4amps could it be the battery ? i'm currently using trustfire protected with the flame packaging..
Is your multimeter getting good readings? mine showed 1.4a before I got better leads.Now shows 2.3a
Think so it;s always been ok in the past, i've tried to run the light on primaries but it hardly works at all on them ...
This is the new driver that i installed
http://www.shiningbeam.com/servlet/the-132/3-dsh-Mode-Regulated-Circuit-Board/Detail
I see that Maplin is selling the decent DX leads for 5x what DX sells them for.
I bought a couple of pairs and tossed the junk ones that came with the meters.
But bought a USB "microscope" in a Maplin sale.
But the light also doesn't seem any brighter in fact i would say it's no brighter than the R5 drop in that i had in the body before
I really think its the leads. Seems to be a common problem. They seem fine till the amps get up,but then just keep showing low readings.
How bright is it? Won't be brighter than an R5 but should give HEAPS of flood.
It is about the same as my R5 but produces a lot more flood so i guess it must be ok..
Don i don't suppose you have a link to those leads do you?
http://www.dealextreme.com/details.dx/sku.33451
I still use the old red one to check voltage saves plugging unplugging 
I got my 501B MC-E today. It's really bright, mostly flood. It draws 2.65A on high! There was an annoying donut hole but I just unscrewed the reflector a bit and now it's not visible at all. I can still make out the cross sign but it's very faint and doesn't bother me at all. I'm very picky about beam patterns, as you may know, especially on my R5-A3 and F23, but the MC-E pattern is very nice.
Nice!! I'am still waiting for the drivers.....
I've gone to the official Ultrafire website and funnily enough they have a bad websites list which are known to sell fake ultrafire products. There are only 2 websites listed there but DealExtreme is one of them. This may explain the lower quality build.
I have an ultrafire flashlight and it is one of my favourite torches, I have ordered more of these torches but different models. I got mine off dinodirect, they even have some flashlight holsters/pouches in the flashlight accessories section.
The ultrafire torch i have now is a smaller version of the 501B called the 501A. With a cree R5 bulb module with aluminum reflector and housing. The torch body itself is made of some nice high grade aluminum with a smooth finish and a nice shiny black coating. The light throw is nice and bright at 20 metres. There is no visible patterns on the beam, just a nice round circle the slowly fades away at the edges.
For those that are curious, the other bad website is Lightmalls, which is a common BLF-spamming website. Here's a link to the "Fake UltraFire Product WebSite List": http://ultrafire-shop.net/page3.php I'm surprised there are only two websites on the list (so far.) :)