I've been using my Leica R8 for seven years and am entirely pleased with it, so I have no inclination to sell it and buy an R9. I use it far more often than my M6 TTL due to the latter's limited (up to 135mm only) focal range. Additionally, based on previously reading a few writings re the R9, there are apparently no significant operating changes between the R8 and the R9. The only problem I've had with my R8 was film scratches, but Leica's New Jersey plant replaced the pressure plate and everything is again okay.
The R8, which was the first slr that Leica itself built since the Leicaflex SL2 in the early '70s, cost the company lots of R&D dollars. It never sold well, being large, heavy, expensive and initially plagued with lots of electronics problems. (Most new model Leicas have electronics problems for the first year or so.) Many feel the R9 is an attempt to increase sales of a "fixed" camera, with none of the bad word of mouth associated with the R8.
The R8/R9, has a beautiful big, bright focusing screen and can be coupled with either a 80mm f 1.4 lens, which is one of the best portrait lenses ever made or a 90mm f2, which is the sharpest lens known to man. I considered upgrading my old Leicaflex SL (1969) to a used R8 but bought a medium format slr, instead.
Both the R8 and R9 will accept the new 10 megapixel digital back, coming out in the fall, making it the first 35mm camera which is both film and digital capable.