bbq,
I have upgraded to the JR DS 285MG servos, and I love them!! They have been great, and survived a couple of nasty crashes with no damage. I would highly recommend them....the DS 287's are the same basic servo, just faster I believe, they call them "ultra high speed" ...
For me, the 285's are fine...I don't do any 3D yet, so I'm probably not going to miss the extra speed.
I can't comment on the DS290G tail servo, since I have never used one....but if it's anywhere near as good as the 285's have been for me, I would say go for it! I have been really impressed with my JR servos.
I chose the Futaba 9257 servo on the tail of my B400, because I wanted to make sure I had enough speed and holding power for later on, if I get more serious with any 3D type stuff. It's a big servo, and heavy, and a bit hard to mount, but it flies really sweet with that and the Futaba GY 401 gyro!
Just keep in mind that when you run 4 digital servos, the stock ESC isn't going to like that at all....they draw more current, and the stock 25 amp Eflite ESC is marginal as it is, especially in hot weather, so you may want to consider upgrading the ESC and/or installing a good BEC at the same time.
The other point worth mentioning is that the DS285/DS287's are a direct drop in installation, no enlarging of the mounting holes required, which is nice....you'll have to use the JR arms, and of course, reverse the servo settings, since they are reverse from the stock Elflite servos.
I don't see how you could go wrong with that combo, I would say go for it!
Good luck with it whatever you choose!
Glenn