There were many engineering recipes dropped between beta and retail release of the expansion, as a result there aren't many recipes available to progress from about 355 to 370, and the recipes that are in game require very expensive materials. Also, most engineering trinkets cease to function against creatures or other players over level 60, so as an engineer levels the stuff they've been using becomes less and less useful with no replacement in sight. To compound matters, none of the trinkets or bombs can be used in arena combat, including even marginally useful trinket pets. As compared with jewelcrafters, who can use all their pets in arenas. The only positive preview we've gotten for things coming for engineering is this post, in which Drysc hints at a frost grenade. Since it's a grenade, and probably a consumable, it's also a non-player in arenas, and since many engineers took the profession for it's PvP utility this is not a very promising development.
I've dropped engineering after being an engineer for over a year. How many engineers are left out there? Why are you still an engineer? Are you finding it has enough utility to justify keeping it, or are you hopeful that there are enough new things coming that it will be once again worthwhile?