The best (and worst) biomass boilers?

Having spent several years looking into the biomass boiler market, I have heard all sorts of stories about which biomass boilers are worth investing in. As with any market where there are many variables, this is not a simple answer.

As owners or installers of biomass boilers (including central heating stoves), which boilers are your favourite or worst?

Please provide make, type, size, fuel feed system and use of boiler, and what you find good or bad about the boiler. If you also wish to say what you paid/charged for the boiler and/or whole installation, please do! Could you also say if you have a back-up or peak-load fossil-fuel boiler and provide some details of this.

There are biomass boilers for all types of situations and wallets. One type of boiler might be built like a tank and will never breakdown, is "cheap" to install, but requires a large amount of manual intervention and (perhaps) is not particularly efficient or clean-burning. Another might be built like a Rolls-Royce, is pretty reliable, burns cleanly and has a price-tag to match, but only needs checking once a week or less and will "speak" to you via mobile phone if it is upset about something.

Some boilers have been on the market for years (e.g. some Scandinavian and Austrian makes) whilst others are newer to the market, and are therefore less tried-and-tested and, in the case of some, are nothing but trouble. Some boilers are known to be better because of their country of origin, e.g. Austrian boilers are often viewed to be the best... but can also be the most expensive. Some boilers seem to be built well and have impressive brochures, features, etc but for one reason or another, have operational issues that only the poor owners end up experiencing after installation. 

Sometimes, issues with boiler operation are nothing to do with the boiler, but instead due to the way the boiler has been sized and/or installed. This will be the focus of a future discussion. However, many biomass boilers, particularly in the UK, have been installed incorrectly and therefore have operational issues, sometimes causing them to be mothballed. These issues can be due to oversizing (more often than undersizing), incorrect plumbing, no or incorrectly-sized thermal store/buffer vessel, poor fuel quality, fuel feed mechanism faults, badly-design controls, incorrect flue design, etc.

Some of these issues are being addressed as we, in the UK, learn more about how to design biomass boiler systems correctly. However, there are still boilers being installed in systems that have faults and will eventually cause the owner issues or will be problematic from the day the boiler is switched-on.