I would actually like to add a couple of points here. Firstly regarding dividing by half decks rather than full decks. It's nothing to do with accuracy and you can use it with the Hi/Lo count. It's called the True Edge method and whilst it is a little more clumsy than the True Count method in terms of it's accuracy, on the whole it makes little difference and many people find it easier. Think about it - if each point of the TC gives you 0.5% edge (approx.) then if you half your TC, or divide by twice as much, you are going to get you % edge. You would have to double your unit to compensate for this, but that's the only major difference this will make.
Deck estimation accuracy - i'm not getting dragged into a long argument about this - we all been there and done that before, but the most i'm ever off by and this isn't very often, is 1/4 of a deck if i judge the wrong way (i.e. it's in between 2 increments and i choose the wrong one), where as if you are judging to the nearest deck, you can be off by a 1/2 deck or more in your estimations. Not an error i'd be happy with.
As to improving your eye, when it comes to deck estimations an excellent method that i've found that really helps is to take your discard tray and tape a piece of black card (so the light doesn't shine through it) to the outside of the narrow side. Stack 13 cards in the tray, get down to eye level with the stack and take a silver or white pen and make a mark. Proceed to add another quarter deck and mark. Repeat. It's a very quick and accurate way of measuring to the nearest quarter deck so that you can check your accuracy.
A word of warning however. You need to change your ruler every time you change your cards. As i said previously, the thinkness of the cards change and this can make a substancial difference. You will get use to changing cards fairly quickly and be able to compensate for different decks just by playing a couple of shoes - it just takes practice.
RJT.
