As far as I know, nothing limits its use even down to cryogenic temperature, i.e. it does not have a brittle-ductile transition like some steels. Some of the more exotic alloys do get brittle at low temps, though. It should not be used in the presence of liquid oxygen, as it can readily burn if cut/scratched/banged.
There is some data on fatigue strength of Ti-6Al-4V, both regular and ELI (Extra Low Interstitial) flavors, at cryogenic temperatures in Materials Properties Handbook - Titanium Alloys by Boyer, Collings, & Welsch (published by ASM International, 1994). There is no fatigue limit with this alloy, as subsurface initiation occurs at > 106 cycles. That doesn't mean it isn't suitable for use, just that you need to understand the loading conditions and relevant number of cycles. As btrueblood noted, there is no abrupt embrittlement phenomena to be concerned about.
