I know you've already stated that you won't provide details on every tweak, but a few of the powers/abilities are just completely mysterious (e.g. Dumner "meet challenges with boldness" or whatever). I even fired up the CS and tried tracing the ability to the script to the token to the token script, but by then I was unsure what I was looking at. Can you enlighten us as to what these mystery powers actually do?
It's MagLite where I didn't fully document every tweaked number. With TRAP, the mysterious unexplained listings in your active effects list are control scripts... they generate passive effects, but all of those effects actually are documented. Meet Trouble With Anticipation (a reference to the Dunmer temple faith) is the ability which gives you magicka when you lose health.
That being said... I can't help but feel like the balance is still wrong. The Thief used to be overpowered, and it's still overpowered: it gives you +45 (!) to attributes, plus invisibility, plus a major power. Compare this to, say, the Ritual: no attribute bonuses, a touch-only lesser power that might help to ward off some creatures (but will enrage others), and two major powers that are cool but still limited in their usefulness.
You would be absolutely amazed at how few people actually show up with feedback on the signs' power levels. Thank you.

I've been uncertain on that one myself... the +45 total on the Thief was an early tweak (back when it was still nGCD Birthsigns, and I hadn't added active powers to those signs).
Something you have to understand, though: from a min/maxer's perspective, simple attribute bonuses considered are
the worst benefit a sign can give because there's a hard cap on attributes and you can reach it with or without the bonus... so at the end of the day, someone with the vanilla Lord is ahead of someone with the vanilla Warrior. Both of them have equal maxed-out attributes, but the Lord has a lesser power.
Now, for a lot of people this isn't an issue. Many of my mods work to prevent you from ever reaching cap in the first place. On top of that, flavor is a bigger design factor than balance in Birthsigns Expanded because it's a single-player game and only the player has a birthsign: you don't have to worry about running around with the Ritual and then getting your ass kicked by someone with the Thief. But the fact remains that the min/max urge is strong in many, it's the perspective pushed by every strategy guide (because they're all for vanilla), and a lot of people find attribute-capping fun and still want to use B.E. So one of the first things I did was push the attribute bonuses up a little, so they were more attractive as an early-game bonus... and since then, it's the last thing anyone looks at when considering balance.
You've provided me with an exception, so it's worth looking at. As I said, the thought has occurred to me as well that maybe Thief should drop back to +10's; its powers are pretty beefy at this point. That would put all the "base attribute bonus" signs at +30 total.
Let's see, which others did you mention...
The Shadow is a balance nightmare, no two ways about it.

It's one of those signs which is almost all flavor... the powers are above and beyond everything else, but you pay dearly for them. It's basically an enticement to role nobody would otherwise play. Maintaining a unique experience for the
one time I expect most people to try it is much more important than making it a "good choice" in a general sense.
The Apprentice's attribute bonus is considered a temporary effect, meaning it can break cap. You also get to move it around. It's far better in the long run, and more versatile throughout the game, than any other sign's attribute bonus. I think it's solid. (In fact, it took me a while to figure out an implementation of the concept which didn't seem patently superior to everything else!)
The Ritual's Spectrum ability is
way better than you realize.

The effect is predictable, is only
potentially undesirable against Daedra, is non-hostile and has no level restrictions. If there's one sign I'm concerned will make the game a cakewalk, that's it.
Lover is also stupidly good, and the +30 Personality has nothing to do with it. There's a reason I dramatically raised the cost of nearly every Illusion effect in MagLite...
My recent playtesting run was with the Warrior, by the way. There's a write-up a couple of pages back about my trip through the Kvatch gate. Clinch is amazingly useful. Warwyrd got buffed to 60 seconds. (...did I release that change? I don't think I did...)
I guess my question is: do you feel as though the signs are imbalanced? If not, what's your reasoning?
Right, after the rambling on specific signs... yes, of course they're imbalanced! There will never be enough playtest data to really balance them, because they're never in direct competition. Theoretical number-comparison never truly reflects gameplay, and if there are improvements to be made they can only emerge from my own and others' subjective experiences, and comments on whether playing under one sign really felt much easier or much harder than playing under another. Of course, even in what little feedback of that sort I receive people have major disagreements on what's strong and what's weak! The more the merrier, of course, and everyone's input is useful. In the end, though, I have to treat this as an art and not a science. "Do you think that sign is too strong or too weak?" takes a back seat to "Was playing under that sign an experience worth having?"
* MagLite
Given the magic projectile speed changes, shouldn't Shock Damage be significantly more expensive than Frost Damage? Frost is almost useless now because it's so slow, while shock is much more valuable. But you've priced them out to be almost the same.
Priced to be exactly the same, in fact. Frost has a unique area effect which generally makes it capable of hitting more enemies than any other spell. Shock is fast, but no longer allowed to have an area at all. Fire provides a halfway point. Each has its rightful place in the thinking mage's arsenal.

TRAP and/or BirthSigns Expanded are not compatible with Realistic Leveling. So far confirmed.
Not compatible how? What happens?