Australia

We have 2 compatible cars. A 2018 Nissan Leaf ZE1 e+ with 62kWh battery, and a 2014 Nissan Leaf ZE0 with 24kWh battery (both Japanese imports). These are total battery sizes, so the usable capacity is lower. The ZE1 seems to be about 50kWh usable, and the ZE0 about 16kWh.

The V2G charger we got is the Wallbox Quasar. It reached end of production in July 2022, and was first approved for use in South Australia in December 2022, 6 months after production ended. I had been contacting everyone I could find to get one, and I was very surprised when JetCharge got back to me a few months later asking if I still wanted one. It took a few weeks to sort out paperwork and logistics, and about a day to install. The unit was about $10,000 and the installation about $5,000 for a total of $15,000.

The Quasar does what it says on the box, but I now understand why Wallbox decided to end production in favour of a new (as yet unfinished) model. The Quasar 1 does not support V2H (at least not well). It has a minimum charge/discharge rate of 6A (1.4kW) so a separate house battery is needed to fill the gap if the house is using less than 1.4kW and you don't want to import or export power to the grid.
It also doesn't have the ability to run during a grid outage. We have a house battery with off-grid capabilities, but we can't legally have the Quasar on the backup circuits because of its ability to overload the house battery. (The same reason the AC and stove are not on the backup circuits).
Both of these issues will likely be fixed on the Quasar 2. The Quasar 2 will be released first as a CCS only model (not compatible with the Leaf), and a CHAdeMO version might be released a year or 2 later, but Wallbox has not confirmed anything yet.

So far I'm happy with the system. It's definitely not for everyone, and needs constant attention to get any benefit from it.
We are currently getting wholesale electricity prices from Amber. Most days we roughly break even on cost, but occasionally the prices spike from 20c/kWh to over $10/kWh. This only happens once or twice a month, but we make more in those days than we pay for the entire month for electricity.
The house battery (10kWh) can export for up to 2 hours, and the car (50kWh) can theoretically export for 10 hours. In practice, the car won't export below 20% (I'm assuming this is a limit in the car, not the Quasar), and it often isn't charged above 80%. This still leaves 30kWh which can last for up to 6 hours at maximum export rate. This is more than enough to cover any possible price spikes, and run the house overnight. The price spikes rarely last more than an hour.

Amber provides some automation for the house battery - importing when prices are low, and exporting when prices are high. They are looking into providing a similar type of automation for V2G. Having to manually set the V2G charger to export during high prices is a nuisance, and without the price push notifications from Amber, we would miss many opportunities to sell to the grid.

The Wallbox app is designed for all Wallbox chargers, and the V2G features seem to have been added as an afterthought. I have encountered several bugs so far, and several design decisions that I don't agree with. Schedules can be set in the app for charging and discharging, but there are bugs with this too. I'm hoping that most of these issues will be fixed before V2G becomes mainstream.

We have a unique situation here. A house with 10kW of solar, a V2G compatible car that's home most of the time, a house battery, and wholesale electricity prices. V2G works really well for us, and I regret nothing. Without these things however, V2G probably wouldn't be worth the current upfront cost.