Like they said, this is an area where there's a decent chance house rules will significantly impact things. For example, my GM decided to nerf Diagnostics by making it only last a very short while (I don't recall if it was all the way down to just 1 combat turn, or a little bit more than that).
You should be able to count on using Gremlins against other riggers to force glitches, though.
Overall, TMs have the potential to become monsters at whatever technologically-focused stuff they do, once they rack up enough karma. They just can't pass off drone command to their sprites. (And essence loss amounts to a soft ban on rigger staples like cerebral boosters, since it costs you your resonance.)
Also, TMs are pretty MAD, so it's hard to make one that starts out being good at rigging and other Matrix stuff. They need high Res for their sprites and CFs, at least 3 high mental attributes for their living personas, and lots of skills already. Adding in hardware (TMs need it, but tend to skimp on it at CharGen), gunnery, piloting, and whatever amount of sneaking on top of that? Something's gotta give - at least in the beginning.