The pronunciation was extremely easy and many concepts made sense. However, even when we got to the 6th chapter it was still impossible to form basic sentences beyond "mi'e .persyn." In most languages, I can memorize vocabulary and fill in the grammatical blanks later... but in Lojban that's impossible. I have to learn the grammar before I learn the vocabulary. Whenever I've looked for Lojban flashcards, they seem to work like this: "x1 is x2 at x3" or something similar.
Additionally, having vocabulary made up from the vocabulary of other words seems like it would be a good idea, but in practice I'm not sure if having "prenu" as a combination of "person" and "ren" helped, -especially- not in the same way that interlingua's/Esperanto's/other European-biased loanwords help. I'm not sure what you can do to improve on this situation, however, and I'm sure you've debated the pros/cons of this vigorously. The vocabulary isn't nearly as much of an issue as the grammar.
And, yeah, back to the grammar. I found it extremely hard to discuss or explain concepts to other Lojban-learners, especially when the book will basically follow this format: "Okay, this is the [x]. For the logicians in the audience, you can basically consider this [y]. For the mathematicians in the audience, you can think of this as [z]." I think constructed languages are an inherently geeky thing to begin with, but those types of explanations struck me as totally out of touch with what constitutes a "beginner".
When we came across concepts that ended up being obstacles, it reminded me of learning math at a higher level, with little help. The concepts are explained in very few sources (I had to look up words like "selbri" and "sumti" on the Lojban wiki because the Lojban For Beginners definition was so unclear), this site is incredibly convoluted and impossible for the uninitiated to navigate (forget asking questions--none of the people in my circle have used a mailing list besides me), and we couldn't speak Lojban outside of our circle because everyone on this site seems to have picked the language up at rapid pace. I think the primary issue here is that most people who have learned Lojban so far at least seem to be extremely intelligent compared to the average person that may learn a language and so it's just expected that lots of things are absorbed at rapid pace (compared to how quickly the average college student absorbs them) and/or understood intuitively.
Finally, I'd like to say something about Lojban as an IAL. From what I know of the language so far, it looks like it would be the ideal IAL by a large margin, but the main issues I see facing it are its complexity and inaccessibility. I've read several discussions about this, and from what I understand Lojbanists usually excuse its complexity at the expense of giving IAL-status a second priority. I think that it's -much- better than Interlingua or Esperanto in that regard, which to me seem like "General European" languages; a somewhat questionable goal, because so many people in Europe speak common languages anyway. Lojban has the advantage of being an inherently better language--if its ease of learning was significant enough that it was comparable or better to a non-European student learning Interlingua or Esperanto, I think it would be a serious contender for the IAL.