Well I pulled the trigger and have had the L1's for about 5-6 days. First the bad, the don't sound as good as the Fidelio X2...the X2 sounds like you are there, or higher end speakers in a good room. I was pretty sure of that before I pulled the trigger. Every day I listen, I really appreciate them more and more (a bit of brain burn in).
I am extremely happy with them. First....the design and resulting compromises are almost perfect for my use of these cans.
Isolation:I wanted some isolation - so with moderate volume most of the office din is drowned out...but without the complete blackout of IEM. This does it...in fact better than I expected, I can even use them while on the same couch as the kids with the TV on (you hear it in quiet passages, but music is enjoyable when on.
Sound leakage: Minor/minimal. Way less than Grados/HE-400/X2 (least of these three). No issues at all in office environment.
Non-fatiguing: No treble edginess....hours with no problem.
Form factor: Materials, size, appearance are exceptionally classy. As a manager, I wouldn't feel comfortable with plasticy or overly large cans...these are pure class. My ears are relatively large and they fit without a scrunch. Form also works great for semi portable, carry with you, wear around the house. The rotating cups allow a quick drop to the neck for a short conversation with someone stepping in my office or the wife/kids. Very comfortable, while warmer than wide open cans - much less sweaty than something like the ATH-M50, works better with glasses than those as well (but not as good as the pillow than is the X2).
Also the pigtail for removal cables...this is the right way to do it for portable or semi-portable cans. While a cup port is preferred for a strictly homebound can, it can cause extreme stress if you leave the cable plugged in and toss it into a bag...not so a pigtail. Leave the cable in, no undue stress.
Sound:Tonally similar to the X2 once I put in a 3dB cut at 2kHz, very nice energy and punch, bass it controlled, tight and extends deep, nothing missing across the board until you get to the "air" in the upper end pushing these somewhere between open and closed for soundstage and openness (um...they are semi-open). Actually - the staging is better and more out of head for me than the Grado SR80s...so not as good as good open, but better than many.
The highs are actually more present than I was expecting - they are definitely not edgy, they are darker, but do have very good detail and extension. Cymbals, hat brushes, snare, all sound smooth and natural (I would even say there is a narrow band where it beats the X2). This is part of the compromise based on the design of semi-open, non fatiguing. Just hits the nail on the head for those who aren't doing short highly analytic listening.
The sound overall has great energy, nothing offensive, fun, mostly neutral with a warm tilt, bass that is fun without flabbing or overemphasis (pretty near Harman curve). They respond well to additional power - the midrange opens up, bass is tighter and distortion is well in check at moderate high volumes. They are much closer to the X2 than any of the other phones I've heard lately (Shure E4, RHA MA-750, ATH-M50, Grado SR80). I feel they absolutely shame the SR80 in every aspect but "air". I'll add some notes after I do some A/B on the M50s.
Truly an exceptional value at the current price, especially for around the home, office and semi portable.