Nick, from my experience you want to hit the hot items inside of that character limit. What are the HOT ITEMS?
Take a look at the first 3 items on this graph...
[ATTACH=full]2504[/ATTACH]
On average, people want access to their tunes through mobile app/devices.
This graph is from a White-paper full of useful stats from the team over at CarStory. Give up some info and in return you can too get the download - http://bit.ly/UsedCarShopper2015 
As for adding the condition, I guess it would depend on the vehicle itself. "High miles but garage kept and serviced at the dealer religiously".
In general I believe you'll be better served by squeezing in the value build items first while taking your time and finesse to describe the vehicles condition. Can you satisfy the shopper through your written words?
Readers always say "the book was better than the movie". Of course it is, your imagination due to more written words are used to describe that particular scene.
As for automatic description builders.. I have a few dealers using SmartComments by PureCars. I've caught myself several times asking the dealer who wrote that vehicle comment? Forgetting they use an automated service.
I would write all the custom comments at my last dealer stint (40-60 high-end, luxury used cars). I took pride and would have some fun with it. When you take the time to formulate some great descriptions, you really get to know your inventory. That's an advantage when you have a customer on the phone or in front of you.
I can recall MANY times I would overhear a customer ask a sales rep "who wrote the short story on this vehicle? They were very descriptive and convincing". Make them entertaining enough to where your sales team and managers actually go out of their way to read each and every one... they too get to know the inventory.
Something you could try... (this is dependent upon your people) have each used car sales reps take turns writing the descriptions. Initially set them up with a template/formate they can follow until they get the hang of it. This rarely works as we know how sales people typically are.
