DaveyBailey said:
Any thoughts on if it's worth it?
Also just ordered an 11-22 lens but already own the 22- after reading all the threads wondering now if that was worth it too.
Are you asking about the flash because the built-in one is not working for you? If you're satisfied with the built-in, great, you save money, size, and weight. If not, nnowak would say "you're not using it right"

I'm not a pro like him, apparently he rarely bounces and claims the built-in direct flashes are more than adequate most of the time, my results are completely opposite. I've tried different things with the built-in flash, including flash compensation, tilting it, and adjusting distance, and the results for me have been subpar to poor. For outdoor fill-flash, it is too weak unless someone is within a few feet, and for indoor bounce flash it is too weak and underexposes, even with 10ft white ceilings. I also recently did a group shot of people trying various settings, and the front faces would be washed out, and anyone behind the front would be underexposed.
I have the low profile 270 EX II attached to the M3, and despite its relatively small size, the flash results have been night and day compared to the built-in. Not only do daylight fills actually work past a few feet, indoor bounces are properly exposed or sometimes overexposed, which can be dialed in. Direct flash shots are impressive, even in group settings. I wish I kept the built-in flash group shot to show the difference (where the front is washed out and the back is underexposed), below is the same group shot after I attached the 270, direct, no adjustments, automatic:
This was a tough shot with sunlight pouring in from the window behind, and no indoor lighting from the other side, so the front subjects were very dark
If you can get the built-in flash working in the above circumstances, great. I couldn't, the results were actually horrific. With the 270, first shot, this is what you get. Here's one example of indoor bouncing with the 270:
This was taken at night, low ambient lighting
Again, if you can get the built-in working in low ambient lighting, great. Really - I rather not have to attach the 270 if I don't have to. But when I can get easy results like the above, I always have it with me.