Endless debates with engineers about whether it will give traffic info in the UK or whether traffic is US only?
Cant resolve this issue for you as this depends on the capabilities of the approach radar system on the ground. I can tell you that I use the TIS capability of the Garmin 330 in the U.S. and find it quite satisfactory. You do lose traffic information as you get some distance from the radar site, but the system alerts you to this. Where I fly, the high traffic areas are well covered by radar. And, as with most TIS/TCAS/TAS systems, it displays only traffic with an operating transponder - most but definitely not all so keep your eyes open!