07 frame shouldn't be lighter by much... judging from crod2005's 2007 rockhopper comp disc's weight of 30 pounds, and my 06 comp disc's weight of 29, even with heavy 5050X pedals, a computer, and a bulky plasticky-rubbery alligator sqeaker.
i've seen a base rockhopper on this forum (other thread), and someone's pics on his flickr shows that the base rockhopper has Acera derailleurs (front and shifters), not sure about rear der though, probably alivio but *might* be acera... a rockshox Dart3, equivelent of the J3 on this year's base RH. the downgrades to the drivetrain (this and last year, base rockhoppers have come with a deore-level drivetrain, shifters, fd, rd and all) may cause the base rockhopper's price to become slightly more affordable, from around 800 cdn to 600-700. hopefully 600 so my friend can get it instead of a hardrock sport disc... so i can ride it
also, the base rockhopper will be 24 speeds instead of 27, as acera shifters don't support 9-speed cassettes (i think alivios for 07 might though).
and all hardrocks and RH's have BG Rival saddles, and those are 70 bucks on the Specialized website. that's one major upgrade i've seen... that i actually want.
and they have a durable matte-finish handlebars and stems now, compared to cheaper-looking shiny-finish that's easier to scratch.
comp disc differences:
06 -> 07
318 Tora -> 302 Tora (slight downgrade b/c of no motion control)
Deore LX Rear der. -> Deore rear der (1-step downgrade, but front der, and shifters remain same)
Truvativ FiveD cranks -> Shimano Cranks (i don't know if this is better or worse)
Roundagon Rotors -> Cleansweep rotors (technically better, and bb5 calipers are black for 07)
SunRims DS2-XC -> Specialized-branded AlexRims (probably a downgrade)
Shiny black finish bars -> Matte-finish bars and stem (more durable, nicer aesthetically, thus upgrade)
Punk design -> tribal design (debatably better)
all-mountain looking frame -> stumpjumper-xc-looking frame (i like 06 better XP)
it would really suck for everyone if prices remain the same though, because there aren't really any upgrades, mostly downgrades. that would mean specialized is losing its bang-for-the-buck value.
edited because the chart spacing I made didn't show up and it was very confusing, added arrows, a little less confusing to read.