You said "sometimes needed". But within an URL the square brackets are mandatory.
Anyway, most users will never see these brackets, because IPv6 was not designed to be used with their numerical values. The IPv6 representation seems complex but it will only be seen in monitoring tools, or when configuring some router. But for applications, they just don't need to care about these details, all they need is to correctly support IPv6 address types when resolving domain names, and not assume that the addresses returned will only by 32-bit long.
For URLs, there's a need to update your URL parsers, but most often this will be part of a library already implemented in your browser. Browsers are already ready, as well as most major operating systems.

So what are ISPs are doing ? all RIRs are ready, and they already urge the LIRs (most ISPs are LIRs) to implement native IPv6 routing in their routers, as well as deploying IPv6 as a dual stack protocol directly usable by their customers.

Unfortunately, most ISPs in Europe still provide DLS routers that only support a single IPv4 router, and don't even offer a free 6to4 or Teredo tunnel, so users have to depend on general tunnel brokers, that are extremely slow.

In next June, possibly even before (because we've seen a recent acceleration to compete for the remaining very few IPv4 /8 blocks, notably from China whose demand is very high). China will be certainly the first country impacted by the lack of IPv4 addressing space (because most other majors ISPs and LIRs in the world have anticipated the need for long by getting overlarge delegations).

In next June we'll see the apparition of a black market where large ISPs in the western world will start reselling at huge prices a part of their delegations. Some poorer countries that don't have large delegations for their ISPs will suffer, and I really think that the last IPv4 /8 block should be reserved for AfriNIC (and european ISPs can already help African countries to build and prepare their infrastruture, given that they already need African call centers and data centers for their daily commercial operations....)

Why don't ISPs in Europe and America really move to offer native IPv6 connectivity to their customers ? This is unbelievable, and soon they will suffer from lack of connectivity with the rest of the world, and will have to support huge costs because customers will complain !

It just remains about 200 days before IPv4 exhaustion. All the softwares needed are ready, they just don't want to deploy it and have still failed to deliver products shipped with native IPv6 stack (notably in the millions of modem-routers that they have sent to their cable/DSL customers).

Customers are already complaining of prices for mobile Internet (ISPs are billing these accesses with very profitable margins, but these margins will fade out very quick if they have to support very costly 6to4 or Teredo infrastructure to maintain the connectivity).

Customers should complain already to their ISPs for their lack of support and early adoption, before they experiment costly rises of their billings, and lack of connectivity with the rest of the world.

The internet infrastructure is now placed in a huge risk of collapsing if not enough LIRs and ISPs provide a native IPv6 conenctivity. When this will occur, the impact on the whole internet will be extremely severe (in terms of performance, lost routes, failing gateways, unreachable Internet blackholes), as this was seen in last August 27, 2009, when a one-hour experiment was conducted by RIR, causing entire TLDs to become almost unreachable (for example the .fr TLD was severely impacted, as well as the .si TLD, even though Slovenia is the Euopean country that is the most advanced in terms of IPv6 preparation : these TLDs were impacted because of major LIRs in other areas).

The European Union really urges LIRs to take action now. I just wonder why there was not just a law enforced in the European Union by telecom regulators to forve all ISPs to respect what they have promissed since long to everyone.

They seem to think that they have enough IPv4 delegations to serve their clients, but are completely forgetting that their clients need to communicate with the rest of the world.

If we want to avoid the fragmentation of the Internet and preserve its openness (that everyone needs), we strongly need and want a full deployment of IPv6 NOW !

And if IPv6 had been more vastly deployed, the situation would not be so much in risk as it is now. Due to the lack of preparation there's now a very huge risk of a severe worldwide collapse of the Internet during next summer (possibly even before if China continues to accelerate its demand via APNIC delegation requests), when the various failures will start escalating at an exploding rate (where each failure somewhere will cause the traffic to be rerouted to another network that will collapse in chain) !

Really, if such collapse occurs, the only recovery possible will be to stop operating IPv4 completely, and those ISPs that won't have any good IPv6 connectivity will go to bankrupcy rapidly as they will have to pay a lot to other ISPs that will be able to reroute their legacy IPv4 traffic via very slow and costly 6to4 or Teredo tunnels.

Those that will win will be certainly the worldwide CDNs, that could also take full control of the Internet instead of ICANN and regulators. And we'll then have to suffer much higher prices for the Internet, or the Internet will become completely fragmented and no longer open. This will be a dramatic end of the decenials of success, with lots of jobs and businesses now placed at risks in a serious worldwide economic situation, where only very few coutnries will be impacted (China will resist, but what will happen to US and Europe ?)

Do you want tomorrow an Internet governed by China in the Chinese way ? NO !!!

So ask to your ISPs an immediate action plan for getting native IPv6 connectivity NOW, even if for now you don't use it much. Nothing serious will happen to your internet connectivity if your ISP has the alternative soltuion if ever the whole IPv4-only internet collapses.