I took up Engineering pretty late with my Warlock, gave up Tailoring 225+ to take it. I basically felt that tailoring had nothing to offer me, I never used any of the armors I could make because there was always something better on the AH. With engineering though, you get to use stuff that only engineers can use, so basically you're making stuff for yourself and yourself only, so you actually kind of feel that it improves your character, unlike tailoring.
So far the most useful and fun things are the trinkets; I have four so far. The Shrink Ray is just a blast, the net launcher I rarely use because it seems to malfunction too much, the jumper cables I rarely use but I keep on-hand just in case (they rez a dead player [unless they explode]), and I just got my robotic battle chicken tonight. The chicken will be pretty cool for tough fights, because with me and my pet, that's a 3 on 1 battle in most situations, and it just looks really cool.
Some of the head-gear and other armor is useful too, and you can use target dummies, dynamite, and other interesting contraptions if you want. I personally don't carry any of this stuff with me because I rarely would use the items, but they're there if you want to work them into your fighting system.
I highly recommend taking up mining for this profession, you will use alot of metal bars, stones, and gems that you get from mining.