Agree completely and look forward to more thoughts on topic of just what makes a 4/5 or a 5/5 night for both seeing and transparency. I also wonder if 1/5 means you should have stayed home and so I never actually log 1/5 as that is a skunk night and not worth observing anyway. 0/5 means it is raining
Seeing is how much turbulence the atmosphere provides between you and the stars and transparency is how much muck is between your scope and the stars. (just to clarify and I know we all know this definition)
For ORs try to specify NELM and SQM as a minimum. NELM accounts for both seeing and transparency but varies perhaps a lot between observers like up to 0.5 or even more. So calibrate yourself to others around you to see where your 'scale' lies. I have found I am about midway for a 50 year old.
If you are patient you can do NELM using the finnish triangles but I tend to find groups of stars that range from 5 through 7 that I know are not doubles and see which one is the lowest mag I can see averted over 50% of the time. I realize this is a 'quick dirty' way but it works ok for my own notes. Finnish triangle info:
http://obs.nineplanets.org/lm/rjm.html
Transparency is the really tricky one. I have a few favorite galaxy groups that have mags from 14.5 to 16 that are easy to find and I see how dim I can make out the faint ones. 15.5 is a fairly transparent night, 16.5 is a total limit of 5/5 transparency and depends on the core and being at zenith in my 18" dob and being at a dark site of SQM 21.6 or so.
I always take a few SQM readings and make a note. It is easy and fast (once you buy the meter). This can easily change over a night by 0.3 to 0.5. Take reading directly overhead BUT avoid the milky way (especially you guys with the galaxy core right over top as it is FAR brighter in the milky way).
Another 'overall measurement' is looking at well know but faint object like up here I use M101. If I can see the faint arms and some of the very dim stars in the haze it is a great night. But this is not very scientific at all.
For seeing all on its own a very rough estimate as mentioned already here is to look for how much twinkling the stars have. Zero means seeing is very good, constant flicker is very bad seeing.
For more science find double stars of similar magnitude with spacings suitable for your scope limits so on a great night they separate very nicely but on a poor night they merge in a fuzzy blur. My very favorite is the double double up north here but you guys have a big scope double double in Nu Scorpius (
http://en.wikipedia.org/wiki/Nu_Scorpii) But you need excellent night to split both sides of Nu Sco. In 'average' seeing it appears as two stars with one being a bit elongated. I have not found nice lists of doubles for all around seeing tests so have slowly been gathering a few but basically for my 18" dob I look for stars about mag 7 that are not too hard to find with telrad and about 2 to 3 arc seconds apart so seeing judgement is easier. Both famous doubles I have listed are naked eye targets from a dark site.