Loads of coolant!! If you take a fine cut, the swarf can self ignite due to friction heat and you can not put it out! I know! Great for lighting BBQs though! Get a load of the finest swarf you can, put some sunglasses on, place in BBQ coals, light with a lighter and then blow it.
Some types of Ti machine lovely, others (Beta C grade in particular) are an absolute nightmare.
Aircraft/medical grades such as TA38 are a joy to machine and can be turned on a small benchtop lathe with no real problems, though drilling can be a bit of a pain.
HSS tools will quickly expire on Ti if run at too high an RPM, but as long as tools are kept sharp and RPM kept low, you should have no problems. I used to machine Artificial Shoulder Joints (and hips and knees) from TA38. The part had a very complex thread pattern, 4mm pitch, straight sided with 1mm land, .5mm rads at root dia, 11mm parallel, then increasing in depth on 2 different radiuses (OD and Root), if you get what i mean, all with an old bit of HSS ground by hand! Used to run it at 60 RPM and use neat cutting oil for lube.
I make Lotus F1 2-part Rear torsion tubes from Beta C Ti and it's a bloody nightmare! Beta C was developed for aircraft springs so you can imagine how much fun it is to machine. For every 20 we make, they reject 12! One part has a 1mm wall thickness and a tolerance of .01mm on the OD over the entire length of the part with a bore tolerance of .008mm.
I also made a load of Ta38 fashion rings when i was made redundant a few years back. It's great for jewelry as it polishes up like a dream and does not react with the human body/skin. I made enough money from the rings to keep me afloat during hard times, and still make to order now! Good earner for 3 hrs work on and old 30mm bar end!
You can also "Anodize" Ti at home with NO specialist equipment! I use 2 Li-on batteries from a cordless drill and some super cheap kitchen cleaner. You can get a range of colours just by changing voltage and duration.
If you do try anodizing, wire up 1 side of your power source (must be DC) to a small artists paintbrush ferrule (must have metal ferrule) and the other side to your lathe. Then simply run at a low speed, dip brush in kitchen cleaner (electrolytic solution) and carefully "paint" your part, be uber careful not to touch the ferrule on the part as sparks will fly and you will burn a big hole in your part.
