I've put 430 logged miles on my Merc now since I bought it in mid April, and I've found it pretty sound. I needed to true the back wheel after I took it touring on rough roads with a heavy load (I was camping), and I found the dynamo needed a bit of fiddling with the contact on the wire the other night, but it still looks great and performs way better than I thought it would. I use it EVERY time I have a cycling opportunity, and I have two pretty good mountain bikes as well.

On the gearing thing. When I first got it, I felt it was over geared, and planned to get a smaller front chainring, but now, I don't think it is, and as I got more confident in it, I realised I could stand up on the pedals and push hard on the 45inch bottom gear and get up almost anything I come up against.

Wavshredr's right about the cost of all the bags and stuff you get free with the Merc. I don't think an M3 comes with much beside the bare bones bike (but you can check on that yourself).

The only thing I really would like are better brakes. I rode my mountain bike the other day and applied them like I do to slow the Merc and I nearly went over the bars, however, that's exactly how the Brompton is.