I can second Mastermind's recommendation of Harmon Vindeur. We used them to replace the windows, and door, on our house about 3 or 4 years ago. We wanted windows with a good U-value, and they were about the only company that didn't treat our question about U-value with derision (several companies seemed astonished that we would want to know how effectively insulated their windows are, some pretty much refused to discuss the topic with us).
Our windows are finished in white. Harmon Vindeur claim that this finish will last about 12 or 13 years before it needs to be re-painted, but only time will tell whether that is really the case. The marketing information makes a big thing of the manufactiring company being environmentally friendly, which also appealed to us. However, although the marketing also emphasises that the wood is treated to effectively eliminate any problems with knots in the wood "leaking" through the paint finish, we have found that some marks (which we presume to be knots) have started to appear on the inside frames over the last year or so. These marks are a pale brown colour. While the windows have been working out very well, this is the one disappointment with them. Right now these marks appear only on two or three of the windows, and are not very noticeable, but it remains to be seen whether they will get progressively worse over time.
So, all in all, the windows have proven to be very good, in spite of the blemishes that have appeared. The company provided us with all of the technical information that we requested, and in addition they were willing to accomodate some odd requests that we put to them (in particular, we wanted to fit a cat flap into a double glazed unit) which most other companies wouldn't even consider (the representative of one company practically told me to sod off when I raised the question with him - I think that was one of the companies listed above, but I can't remember exactly which one it was offhand so I won't name names for fear of getting it wrong). I would use them again, but I would probe them first on the manufacturer's guarantees on the effectiveness of the paint finish and what comeback you may expect if the finish does not match its promises.