In the particular instance i mentioned the TCAS was really helpful as i was level at 1200 there was a scattered layer between 1700 to 2000 and the other traffic was showing at approximately 2300 to 2600 so a visual may not have been possible.
As you have noted, you have PCAS - a non approved avoidance aid. The aircraft that I fly has TCAS 2 change 7. Believe me, it has it's limitations. It's very nice to have, but no substitute for the Mk.1 - even at altitude. As Mad Jock said, it is not fantastic at lateral. We often 'see' targets or proximate traffic jumping around the screen, doubt there all fast movers doing supersonic speeds! The altitude readouts (we can select relative which is usual, or absolute alts) always seem accurate. It's always fun in RVSM being 1000' separated from another jet especially if it's a heavy. Had a yank in Houston say to centre controller "we got him on the fish finder"...
In answer to your question, yes, it's ten fold better than a PCAS system. It's a great SA tool. Rest assured, we still maintain lookouts. A controller won't let us (correctly so) maintain our own separation based on it. Visual is visual in a non radar environment, end of.