Is a rangefinder right for me?

I've used SLR's (an Olympus OM-10) now for the last 8 months. I'm looking to upgrade my camera, and was liking the Leica M6. However, ive never used a rangefinder.

Most of my work is [candid] street photography.

Is a rangefinder hard to use? Will I be able to focus fast enough to catch what I want?

Thanks!

Well from what I've read on the 'Net it looks like a good camera. I used a rangefinder ('69 HiMatic 7s) for awhile, before I picked up my SRT-102. They're good cameras, and the focusing is fast, once you get the feel for the camera.

The Leica M has conserved its general features and ergonomics from the first produced M in 1954. 50 years does not change a camera because the features are user tested and approved to be most appropriate. The M6 is easy to focus and the lenses are pretty short throw and many are conveniently tabbed for 1 finger focusing.
Problem with the M6 is rangefinder patch flare out of all things. That is, the light strikes in a way that flares up the rangefinder patch so that you cannot superimposed the 2 images making it impossible to focus in certain conditions. For this reason, you may enjoy the M1, M2, M3, M4, M7(later serial#), new MP. However, only the MP and M7 are metered cameras. You can upgrade your viewfinder to the ones that do not flare as readily, but that will cost you lots of money and is only available at very select repair shops. The M6 also doesnt have a self timer like the earlier cameras.
The M6 also comes in 2 editions, the TTL and classic. Both have in camera metering, but the TTL has TTL flash metering. The viewfinder is also available in 0.58x 0.72x 0.85x magnification. 0.58 if you enjoy using exclusively shorter focal lengths or wear glasses (28-75). 0.85 if you enjoy using normal to telephoto (50-135). 0.72 for the best of both worlds. Remember that higher magnification increases your focusing accuracy with ultra fast lenses such as the 50mm f1 noctilux or 75mm f1.4 summilux due to the increased effective rangefinder base.
I have a rangefinder myself and it's very easy to use. Leica is very intuitive. However, they are very expensive. Perhaps you would like to share what focal lengths you are interested and the speeds required, plus the amount of money you would like to spend? Many of the old lenses are still superb, but cost a fraction of the new amount.

It might be best to try an inexpensive one to see if you like it first. I have a Canon GIII QL17 which is a great camera that can be had for under $100. Only problem is that it uses Wein Zinc Air batteries because the Mercury batteries originally designed for it can't be sold in the US anymore (environmental reasons). These batteries are a little expensive, hard to find and don't last as long as they should. I buy a few of them from time to time at B&H for about $4 each, that way I've got them. Non interchangeable lenses, but the 40 f1.7 is pretty sharp.