I am hot and cold on Brussels. I really want to like them but I have 2 of their extra large trees, one Chinese elm, the other a ficus and they both have deep wire bite in the trunk. It is a little unfortunate, especially because they were some of the more expensive trees. :/
Of the many difficulties I have encountered in bonsai, finding good starting material is up there and has remained somewhat elusive. Granted, I am not spending thousands on a tree (money aside, I'm not sure I can care for it and not even sure what I'm looking for at that price), but I haven't exactly been shy about the spending either. I have otherwise tried all manner of starting material. And have come to some odd conclusions based on my particular experiences and NY prices.
I enjoy going to my local bonsai shop, but it's really a glorified nursery. I know nothing about bonsai and manage to teach these guys something every time I go because I think they are somewhat clueless (the ability to airlayer a deshojo, for example, shouldnt be a surprise to someone in this field for so long). There is a great selection of really young trees, but no bonsai work has been done to them. It's a stick in the dirt that they charge no less than $60 for. Their soil is miserable and they insist on repotting the trees into bonsai pots and packing in the organic soil. I do not even let them take it out of the nursery container and they give me a few bucks off for saving the pot. A trunk with any type of character is rare. And the specimen trees are full of really ugly grafts and really no branch work - its just a bigger version of the stick in the dirt.
Nursery stock could be great depending on price and one's ability to find something decent to work with (as well as an appetite to start anew on nebari). I had little luck in this department and NY nurseries are very expensive (like $600 for a smallish coral bark maple with awful grafts). I tend to hit the nurseries after Halloween when things are half off. Still expensive for what I'm getting and I really haven't seen anything that screams "bonsai me, please". The 2 good trees I got at nurseries I butchered - that's on me.
I'm still a big fan of the Home Depot maples. Granted, I've managed to butcher these as well, but I have not given up hope. I believe I can make something decent out of one of these. And at $15/tree I will sure as hell keep trying. From my experience, the difference between a $15 HD maple and a $1,700 JM from Brussel's, for example, is just not worth it. I believe I can get the $15 HD maple into a decent pre-bonsai in a few years and save myself a boat load.
I have field grown trees and seedlings from a range of sellers. I've mostly been happy, but these still need a good deal of development to get them into bonsai mode. I pulled the trigger on one giant BC and that will be my prized tree for now (as soon as it makes its way to NY and not in the winter).
Which brings me to Brussel's. As for complaints, many of the trees are "S" shaped and kind of typical. But that's not really a complaint. I need to learn the wheel before I can reinvent it. I have no new bonsai style to introduce to the world just yet. I'm still getting my bearings. Frankly, extreme trunk movement makes it easier for me to imagine where branches will one day be. There are many up sides to Brussel's, IMO. At around $350, the trees have a nice trunk caliper. There's movement, of course, and even some taper. But best of all, when I removed the moss there was an actual nebari.
I feel like I actually now own some pre-bonsai (as opposed to the step before pre bonsai). The form of the trunks is done. I will need to add taper with some sacrifice branches, potentially shorten at least one of the trees, and get started on branch work. The trees are on their way (provided they survive this winter). When I first saw Brussel's prices I had sticker shock. I now view most of these as good deals. The JMs are still ridiculously expensive. I also haven't gotten into pines just yet, so I just skip over those (that may be where the wire marks are most prevalent).