If anyone is questioning whether or not to buy a certain brand or model, I *highly* recommend searching the sewing machine reviews
at PatternReview.com. You have to sign up to read reviews older than six months, but they don't ask for any personal information and I haven't seen any spam in my inbox since I signed up almost a year ago.
The Personal Experiences:
Currently, I'm using a Kenmore 16231. I hesitate to post any sort of glowing review as I've only tackled a few smaller projects with it and haven't forced it to chew through multiple layers of denim or vinyl yet. But so far? I have found it to be an extremely reliable machine that offers a fair number of features for the price I paid. I've had no problem sewing through multiple layers of standard cosplay fabrics: cottons, Casa satin, organza and the like. Stitches have been straight and even on all the fabrics I've sewn and I've never had a problem with the tension or bobbin. I rather like having the needle threader and thread cutter (didn't have those on the ancient Singer I used to use!) and am getting used to the speed setting, but haven't had much use for the start/stop button (much prefer the good old fashion foot peddle). The only thing I dislike so far about the machine is having to hold the handle down to back-stitch.
I have also used the Husqvarna/Viking Lena and, while it was a fairly basic machine, I found it to be quite trustworthy and very easy to use. Given a couple days, I even got over the fact that their measurements are all metric. =P The downside to buying a Husqvarna is that they tend to be more expensive than other brands offering similar features.
On the other end of the review spectrum, I avoid new Singer machines at all costs. While they may have once been THE brand to buy (and I've enjoyed working with very old machines), I have had nothing but grief and frustration with the newer models. The Featherweight in particular has been the bane of my existence - from the moment it came out of the box, I had issues with the thread tangling, jamming and snapping that no amount of adjusting tension, switching bobbins or cleaning the machine could ever fix. Even took the thing to be professionally serviced and it was still throwing fits. A slightly older Singer (sorry, have no clue what model it was - something from the early 90s) I was using before that suffered many of the same problems. After adjusting everything that could possibly be adjusted, I gave up and bought the Kenmore I have now.
I also avoid White and Brother after hearing similar stories of bobbin and tension woe from other people. (I do have one seamstress friend who LOVES her White, but she's the only person I know who has had good experiences with the brand.) Someone once told me (don't know how true it is) that Brother bids out their contracts so one year they might have a great batch of machines, but the next year they might be made by a different manufacturer and all turn out to be crap.
As for Bernina, the people that have them seem to love them, but I can't justify spending that much money when I only sew a few things each year. If you are an award-winning costumer who plans on really churning out the costumes year after year, go for it. But the average cosplayer who just wants to dress up like Sakura or Orihime or whomever is the fandom favorite of the moment? Would probably be better off looking for something a little bit less expensive.
As for me, I'm entirely self-taught and have been sewing off and on (more off than on) in my free time for over ten years. Most of my projects have been fairly simple - a couple skirts and dresses, random costume and clothing odds and ends, and one notoriously difficult coat. I've done some pattern adjustments and a bit of drafting, but nothing TOO serious. I suppose I'm an advanced-beginner, maaaaaaaybe an intermediate sewer.