It's hard to know what to believe Robin, some of the negative stuff I have read is from people who have absolutely no experience with any kind of machinery what so ever, probably bought because they thought it would be an easy and cheap(ish) way to make lots of money.
From someone like yourself I would expect to get a more balanced view of the machine.
The tubes probably don't last as long as on better quality machines but if they are a lot cheaper & you have the ability to change them yourself (which you do) then it might not work out any more expensive to run than a more upmarket machine.