There are several top-end, professional-quality digital cameras with more megapixels than the M8, so if that's a primary criteria then it probably isn't cost-effective to trade up from the RD-1. Likewise, if you are the type who will be livid with rage or green with envy if Leica soon releases an upgraded model that does not need accessory IR filters to give reasonably good color rendering and if the current M8 is not upgradable it and the stack of ~$100/ea. filters depreciate heavily before you've had the opportunity to realize sufficient cost savings from film/developing. I admit that's part of why I nixed the urge to buy an M8 and in fact bought an RD-1 refurb just recently. Waiting and watching.
As a new RD-1 owner and an almost M8 buyer, I am first to say it's not all roses with the RD-1. Since you have one and it's working, I'll assume the reliability and service issues haven't been a problem for you. Certainly there are enough sporadic reports of teething glitches with the M8 that it can't be called all that reliable yet but it's so early in the game, in a few months that should all be history (if the M8 isn't as well). But at least Leica has an identifiable service department and acts like a company committed to a product--something that can't be said for Epson in the case of the RD-1.
The M8 has several distinct advantages to my mind. Whether image quality is one or not I can't say, because nothing I've seen on the 'net looks to me any better than any other contemporary digital. You'd really have to compare prints made by people with credible post-processing skill, not uploads sized for the web.
One advantage is the relative crop factor and the viewfinder. The RD-1's 1.5x translates focal lengths to weird in-betweens, whereas in most cases the 1.33x of the M8 bumps them very close to the next-longest common focal length. In addition the RD-1's framelines go only to the 28mm lens which is a 42mm f.o.v., so if like me your most-used lens has been 35mm, you need a separate finder. I didn't mind with the ultrawides, but for my "standard" lens I'm finding it a PITA. Also the rangefinder area in the RD-1 does not move along with the parallax framelines so at close focus it's way off center.
I also find the manual shutter winder of the RD-1 a ridiculous nod to nostalgia. The camera needs batteries to work, and there's no film to move. All the manual lever does is slow me down.
In all I was mightly happy with the M8 when I had a chance to handle one, and just bubbling over with anticipation to get one. Then I found out about the need for IR filters in color and all the excitement just vanished. I'm content with the RD-1, especially at the $1395 price, for the meantime as it allows me to use my Leica lenses on digital while I wait to see if Leica steps up with a revamped sensor IR filter. If they don't by the time the warranty runs out on my RD-1, with great disappointment I will sell all my Leica goodies and resign myself 😀 to a full-frame Canon dslr.
I have been using Fred Miranda's sharpening and uprezzing plugins meant for the Nikon D100 (which uses the same chip as the RD-1) with good results up to 11x14 which is as large as I ever print. I suppose they do nothing magic, but I am not really excited about going through a trial-and-error curve to DIY in Photoshop with a camera most likely I won't have a year from now.
I can't understand anyone committing almost $5000 sight-unseen to a camera, based on what other people say--good or bad--on the 'net, though it seems like that's what a lot of people have done. A few have sent theirs back or sold them, most are keeping them and using them and seem to get overly defensive when anyone suggests they are in any way flawed so I have to wonder in their heart of hearts how happy they really are, no matter how strenuously they try to convince others (and maybe themselves). In any case, the important IR filters are in very short supply, the major firmware upgrade (1.10) is still not ready for downloading, and various and sundry other bugs are surfacing here and there. If you have a good working RD-1, I can't see where there's much of a downside to waiting a few months to see what shakes out.
