Audiologic owner's...

Do you go balanced on both the Inputs and Outputs or not?
I had Jerry take out my AES/EBU input and replace it with a second coax input, as he felt that it was hands down the better input at the time and I needed a second RCA input from a DVD player that output 24/96 digital signals. My unit doesn't have balanced outputs, so can't comment there. One of our members swears by taking the bnc digital output and rewiring it to make it a bnc digital input.
I have an older unit, M34SB, so the balanced OUT is not an option for me. As for input, with all of the usual disclaimers, in my system, with my gear, for my tastes, etc, at one point I made a comparision using identical cables (brand, length, etc) between Coax and AES/EBU, and in my system, the AES/EBU connection was clearly superior. JO has told me that Coax is superior, and in truth that is what I wanted to just didn't work out that way.
Have you guy's installed bybees at any time?
I haven't. In all honesty, I don't recall anyone posting on AG regarding using them with AL.

One other thing I will add regarding input connections. When I spoke with JO, I intentionally asked him about ST-Optical and he was not particularly positive. I thought at the time that in the M34 manual that he had made some comments about it, but I could not put my hands on the manual when speaking with him. Later, I found the manual. Quoting from a portion of a paragraph on the page titled "Read Panel Interace"; "We recommend galss optical fiber".

Unfortunately, I can't use this right now as the ST-0ptical output on my transport is DOA. :o( I did have the opportunity while testing another transport to use the ST-Optical input on the M34, and while I admit that I only had a short time with it, it sounded VERY good. Anyone else using ST-Optical?
I am using balanced inputs and outputs with an Audio Logic 24MXL. As my Levinson 39 transport works best with a balanced output and my Levinson 380 preamp works best with balanced input (and output) I never have done a direct comparison of balanced versus unbalanced with the exact same cables to determine if a difference was distinctive with the AL 24.
I can tell you this. The AL24MXL put the DAC output of the Levinson 39 to shame and that was why I bought it. The only time I have heard my AL24MXL with unbalanced outputs was when I took it to a friends house to A-B it to a Theta Gen VIII DAC. I think the Theta had an XLR output and the Audio Logic had (out of necessity based on available cables and inputs) a balanced output. The Theta smoked it - particularly in the articulation and tightness of the bass.
However, I would still want to run that same test in my own system, with all balanced cables, before I will flat out concede superiority to the Gen VIII. But at twice the price, it SHOULD be better! But once I get a chance to make that comparison, the Gen VIII may be next in the ongoing upgrade path. That or the dCS Elgar.

Generally speaking though, I don't know one instance of balanced cables HURTING the sound quality (all things being equal), but because of the internal design of some electroncis, I have heard unbalanced operation that was clearly inferior.

I hope this helps.
Is you friend with the Theta a member BAAS? If so, he did a review on a site that basically trashed the 24MXL.
balanced dacs stages are a great question..

how many dacs have a dual differential output topology ?

a true balanced circut will increase the db(gain) and lower the floor noise due to cancellation...
Having just had my 24MXL repaired (a transformer went) I gather that the balanced input is a bit of a trick one and isn't actually truly balanced!