tl;dr: DT has some good content but is a PITA to get to. Rigger 5.0 is a great book with a few flaws.
Overall I'd agree that DT is weak. As to it being worth $12.50 is not something I can say. I don't know how important $12.50 is to anyone but me (and it's not my business). I bought it at full price like I do for all of the books as I'm hoping to throw money at the problem of bad editing. Maybe if we buy enough stuff they'll get better? I know it's not good economics, but wishful thinking works sometimes. Right? Maybe? Dunno.
Anyway, there are useful things in DT. There are rules for customizing commlinks and decks that I like as well as the repair rules and such. I'm a bigger fan of the Deep Run stuff than RnB is. I think it's well written. Some of the weird things are that TM's are better suited for doing DRs than deckers are, but a TM needs to spend at
least 13 karma and then
NOT take any of the other much more important echoes in order to take non-TMs/deckers on a deep run with them (as you need to be running a special program). Or, a decker can spend the ¥200 and give up a program slot to bring others along. They point out how TMs and Deckers can work well together (which isn't new, but most groups don't see a reason to have a decker AND a TM which I more or less agree with).
As RnB pointed out there are some good positive and negative qualities. Also, they flesh out AI's reasonable well. That said, I've yet to be able to make a PC AI to my satisfaction. It think they have a lot of the same problems as TMs in that it's a great idea that wasn't fully thought out. That said, they've much more in depth rules for AIs than the do for TMs. DT did not help TMs very much.
Finally, if you are interested in the CFD storyline there's a lot of stuff in there for that as well. There's a "cure" in there that requires at least 1 TM and probably several deckers in addition to the rest of the team running in meat/astral space. Ryo's 3rd world artifact may come in handy if it works in both directions here as they don't go into how to get the old persona back. Just how to get the AI out.
And lastly the ToC is a joke and there's no index. Okay, that's putting it too kindly. The ToC is literally a waste of paper/bits. The chapter names are fluff not crunch so you can't tell what's where. I
LOVE SR fluff in the books, but this goes too far even for me.
(image under spoiler tag)

Luckily I just use PDF for everything, so [ctrl]-f ftw. Still not great.
Rigger 5.0 is a great book. The editing errors and typos still piss me off, but at least that's all errata-able/fixable with re-prints etc etc. The quantity of fluff to crunch is perfect in my opinion for the most part. The exception would be the vehicle descriptions. A lot of the descriptions talk about built-in gear and such that I've not found the crunch to describe :/ But IMHO that's things that a GM can fix/house rule easily. Shouldn't
have to do that, but it doesn't ruin the book for me. The ToC is the same quality as in CRB and they've great tables in the back, but no index. Again, PDF makes it so you don't really need an index and having a fully functional ToC makes it easy to navigate to topics.
I want to make a decker/tm/rigger type using a Horizon-Doble Revolution with a rigger cocoon in it. MMMM recumbent giant wheel with armor... so sexy!