Despite the adverse publicity on here, I installed a Magnaclean around 18 months ago.
I installed it as I was upgrading my boiler and a few radiators, and therefore flushed & cleaned the system a few times before I fitted the boiler.
For the first month or so, I cleaned opened up & cleaned the Magnaclean regularly, and now I only do it every 3 months or so, or when I'm bored !
About a month ago, I drained & flushed the system down again, and I was amazed at how clean the system was. Its now refilled and dosed with Sentinel again.
Does the Magnaclean work - absolutely ! Despite the pipework & some of the radiators being around 10 years old, its really made some difference to the system water quality.
Does it or the valves leak? No, well mines don't, and I've had it opened for cleaning more times than it was probably intended.
Takes a few minutes to islolate, clean & refit, so all in all, so I really cant fault it.
http://www.youtube.com/watch?v=OGckHJIaAW0
Sure it only captures magnetic particles, but anyone with even limited knowledge of chemistry will understand that iron oxide or ferric oxide (both known as rust) are magnetic, and probably 99% of the stuff circulating in a CH system, is just that.
From the adverse reports on here, it looks like some folk have had problems with the valves leaking - to be honest, they are bog standard ball valves, and from memory they were updated about 2 years ago to new ones. So I cant see why they would leak, unless they've been mistreated.
At the end of the day, you would of course be better with a magnetic/non magnetic particle filter, however the Magnaclean does a good job - well for me anyway. Its also down to cost, I got the Magnaclean for £50, and fitted it myself. I think the Spirotech Magnabooster is around £90.
The only downside I can see with the Spirotech Magnabooster type dirt collectors, is the magnet isn't very big compared to the Magnaclean, which is absolutely huge !
I'd be interested to see a comparison between the 2 on collecting magnetic particles. These videos may give you an idea how well the Magnaclean collects iron oxide:
http://www.youtube.com/watch?v=XcoDN6MXu6g
http://www.youtube.com/watch?v=708v9fWLh04
http://www.youtube.com/watch?v=pmiOqkgnrHI
Like everything in life, there will always be opinions for & against, so I've offered my opinion to help in your deliberations.
Hope it helps.