Well, when you throw in the Turning Points series on top of the Touring the Stars materials you've got about 30 planetary maps done and another 1,970 to go >:D. In another half a century we could have an entirely mapped out Inner Sphere :D
Although, we do have a surprising number of worlds that we have data on. I worked it out once but I believe we have almost 400 with stated populations and economic data from all the sourcebook material from over three decades of publications. You can pretty much pick a planet at random and have a 20% chance of finding a write up on it. I honestly can't think of any fictional universe that is fleshing itself out in this kind of detail.
On a side note I would a Touring the Stars for one of the Clan Homeworlds like Huntress or Strana Mechty.
P.S. Just to see how fleshed out things are I took a trip on Sarna to Terra from Lost and using Tharkad as the half way point. In the Nine jumps it took to get from Lost to Tharkad 3 of planets had full write ups with populations and histories, from Tharkad to Terra 6 of the 12 planets had Full Write Ups with one having a less detailed write up from a novel. I could tell you the atmospheric compisition, technological progress, and population of almost half the worlds between Lost and Terra. That is a crazy amount of detail for a universe with 2,000 planets :o.
