I have a 20 litre BM and the only problem that I see is the capacity of the malt pipe only allowing a beer of around 1065 gravity before having to add sugar or other adjuncts to get a stronger beer.
There are ways around this that I wont go into here but you can easily get the info if you search around.
After having had a 3v Herms system I would never go back.
The repeatability, the accurate mash schedules, the not having to watch the process leaving you to do other things while brewing, the fact that you don't have hoses and connections that create a mess and have to be swapped from vessel to vessel during the brew day, the small space that the BM will occupy and last but not least, the ease of cleaning when compared to the 3v all go to make the BM a very attractive proposition.
Some argue the price factor but many like myself started out small and built up my 3v and if I personally totalled what I spent to build a reasonable 3v sytem over the period then the choice of a Braumeister would have been a " no brainer"
I'll just run out now and get my flame suit ready as I have a feeling that I may need it.