A guitar is a strange beast to tune with an electronic tuner. The needles or lights will jump around telling you decisively that you are sharp, flat or right on pitch. The reason may be that a guitar is a great big box with a lot of harmonics, overtones, what-have-you.
Having said that, I use an electronic tuner and I love it. You just have to get used to it. Every guitar has its own tuning quirks, so any guitar's relationship with a particular tuner will also be quirky. I have to stike a note and sometimes wait a second for the tuner to settle down on a pitch (usually). You just get used to it. If I use someone else's tuner I have a lot of problems because I haven't figured it out.
I recommend getting the simplest tuner possible--try to get one with just 3 lights (sharp, in-tune, flat) A virtual or real needle is too prcise and thus to jumpy given the overtones. You don't wand too much information, and you will have to do the final "fine tuning" by ear anyway.
One other thing: I use a contact pickup to run my guitar directly into the tuner so I don't have to use the built in microphone. You may have to buy this separately. Mine is built into a suction cup (I don't think I can spell suction, but you know what I mean) that I slap on my pick guard. It makes the signal a lot more stable and allows me to tune my intrument even if I am sitting in between a piper and an accordian player is a spirited session.