First of all, I want to thank you for your very informative review of the FS4000: it was instrumental in my decision to buy it and...to stick with it! (see below)
Here is my story with the FS4000: I bought the FS4000 from Delta International one month ago, after selling my FS2710: one of the features of the FS4000 that made me buy it was the presence of an IR channel, which the FS2710 lacked.
On the other hand, I was a little worried about the numerous reports on the problems with manufacturing defects. Unfortunately I was right to be worried: the first FS4000 that was delivered to me had severe problems with the IR channel. After 10 to 20 minutes of usage, it seemed that the signal from the IR channel would fade away, and the IR cleaning feature would stop working.
I promptly returned the unit for an exchange, which I got the same day. This unit's IR channel worked fine. But (there's always a but!) I started experiencing the "bright-lines" problems that other users reported, included Nicole Vincent on your site. Once again, I think your site was instrumental in circulating this information among FS4000 users.
Reading about her experience with Canon Australia, I too concluded that the problem was caused by either a manufacturing or (even worse!) a design defect of the CDD. I went back to Delta, and got this unit exchanged too.
Unfortunately even this unit shows the same problem, which makes me believe that there is some underlying design quality problem with the CCD. Luckily Ed Hamrick managed to "patch" the problem by having Vuescan perform a dark calibration, which corrects the problem.
Or at least, it does with my unit when used in 1-pass or long-exposure-pass modes. There are still issues with Vuescan's multipass mode and the FS4000 (as reported by Nicole Vincent on usenet). However, being quite happy with the results of the long-exposure pass mode, this doesn't really affect me.
Now, coming to what I learned from this experience, and ultimately what I wanted to share in this forum:
1) Kudos to Delta International for the way they handled all this: they gained a new very satisfied customer.
2) As it stands now for me, the FS4000 with Vuescan gets me excellent results, especially when used with two of Vuescan's most useful (in my opinion) features: grain reduction and long-exposure pass. In that case it is possible to get very noise-free (and VERY sharp) scans from slides.
3) You were right: if you manage to stick with it, and not to get crazy with the FS4000 and the high percentage of defective units that Canon put on the market, this is a wonderful scanner for the price, especially when used with Vuescan.
Again, thanks for sharing your experience with the FS4000.