Having just got to Silver , I am enjoying the novelty of benefits like lounge access, seat selection etc. for the first time so for me it is good enough. Gold would be great of course to get into the F lounge, access to the spa and Arrivals on long haul, the extra seat availability and the many "soft" benefits but having to fund most of my travel myself it is not something I would go out of my way to pay the extra for.
If we had the "TP runs" that are often mentioned here where you can basically jump tiers for less than £1k for 2 days of flying across the US and back then I might be tempted but being in London it doesn't seem as achievable.
If I was with a company that jetted me around longhaul business class then yes I would definitely aspire to achieve it but with my air travel largely being for leisure purposes, Silver will do. I've never discernibly felt "junior" or treated differently to other passengers in premium cabins well apart from being younger and my hair still its original colour!