For the record and to correct the comment made in the first post
"Probably a lovely euphonic sound more than neutral, linear."
The SE40 is not overly euphonic nor does it sound particularly "tube-y". It is very neutral, especially in the midrange. It's single ended. Some of the best midrange reproduction, solid state or tube, that I've ever heard. So clean, it will embarass many amps as veiled and muddy. It just sounds good, not good for the price or good for an entry level tube amp.
Most people who say bad things about the SE40 are people who have never owned or heard it. It's just plain careless and useless.
Yes, reliability is a concern, but it depends. I've owned four SE40's over the years. Three were perfect, one had some problems, but nothing any competent tech or DIYer can't fix.
Another useability concern is that it is somewhat of a pain to bias. It has to be turned over and the pots are too sensitive and requires use of long plastic screwdrivers.
It also runs very hot. Great space heater for winter. Tube life is not as long as some, need replacing every two years or so.
All in all, the SE40 is a great amp, underrated, sometimes maligned, but loved by those in the know.