I really liked 0.9.9.6. Sure, it had some glaring bugs (Fireangel didn't work, some enemies were "too smart", liquid spawning problems), but other than that, I think that 0.9.9.6 siginfied the climax of the "modern-age classic" DoomRL.
I mean, Classic DoomRl was when you had the 10 levels and no special levels and just the Cybie to deal with. The "modern-classic" DoomRl is the one like 0.9.9.1 to 0.9.9.6, the one with 11 special levels, all the same, not much changing, same exotic/unique weapons/mods/stuff, and similar assemblies all the way.
Sure, I like 0.9.9.7, but I feel that new special levels change the entire feel of the game. It's like playing Inferno for the first time--you don't know what's going to happen, you're caught off-guard, and you feel kind of lost, now that your usual routine has been overhauled.
I would really like to see a "0.9.9.6" mode in new DoomRl versions.