I agree 100% with the XP observation.
I re-read some of my MERP material last night. The XP system rewarded the use of skills for sure- and spells for that matter. I rarely use XP in truth. Our games are infrequent enough that I basically advance a player character based on how many sessions we play and speed up the story line. After 1 session you advance from 1-2, after 2 more sessions you advance from 2-3...etc
I guess what I miss is the mechanics being a part of the dramatic process- something that the MM tables and the SM tables in MERP and RM did well. You could use them toe simulate actions taking a few rounds to accomplish due to partial successes. But, more importantly, because they were used as the core resolution mechanic- adventures were written taking them into account.
As a GM (and I consider myself to be a good one) I believe that all characters need to have a chance to shine- and always write a skill based challenge or two into a session....but, maybe I am the exception not the norm. One of my frustrations with 4E for example was that my Rogue only got better at combat powers every level, his skills improved every other level.
When I was drafting the linear development for the Novus Hack- that was one of my considerations. Getting better at what you do every level.