If you're in the market for sound treatment, then you've certainly come across the Auralex name. They've been a staple in the industry for ages, and their product range is vast. Their ELiTE line is relatively new, and ELiTE ProPanels are Class A fire-rated, rigid fiberglass, sound-absorbing panels with chemically-hardened edges and wrapped in acoustical fabric. Ready-made ProPanels are 1'' and 2'' thick, available in Sandstone and Obsidian (basically tan- ish and black-ish), but custom ones can also be ordered in 1/2'' and 4'' thicknesses, with hundreds of fabrics to choose from. Whether you go ready-made or custom, ProPanels have a polished, professional look that won't detract from an already-established design aesthetic of a room. And unlike the foam-based treatment often seen in home studios, ProPanels have a much wider range of absorption, reaching two octaves lower in effectiveness than acoustical foam of comparable thickness.
Over the years, I've used many types of sound treatment - heavy curtains, prefab panels of different kinds, DIY absorbers, freestanding panels, acoustical foam, etc. - and ELiTE ProPanels have definitely been the most functional, easiest to employ, best looking, and most durable option of the lot. I've honestly still got materials lying around for several unfinished DIY sound-treatment projects. I guess your personal opinion on DIY would depend on how handy you are and how much time you've got on your hands, but I found that I just didn't want to mess with cutting out mineral wool, sanding down frames (I even bought the frames pre-fabricated and haven't managed to stir up the motivation to finish any), covering with fabric, and stapling/nailing/gluing the fabric down. Heavy curtains can look nice and be really interesting visually, but they're less effective than rigid fiber treatment, and worse, they can muddy the room by absorbing too much high end without touching the lows and low-mids. Freestanding options can be useful since they're mobile and placement is simple, but they can also look out-of-place since they're obviously an afterthought in the room.
I've been using the same set of ProPanels in a number of different rooms for a couple years - having even relocated 500 miles with them - and I'm surprised at how durable and simple to move around they are. I thought for sure I'd find a few cracked or split, but all survived the move without even a ding. They go up in minutes; the panels simply slide down onto metal impalers that you screw onto the walls. In one room, I hung several from the ceiling by threading thin metal wire through them at the corners and tying the wire through small eye hooks screwed into the ceiling. I'm not sure if Auralex would bless this type of installation, but I didn't want to permanently attach the panels to the ceiling, and I wanted to angle some of them, so this seemed genius to me at the time, and the results have been great. The panels were dense enough that the shape isn't affected at all by the wire I've passed through them, but they're also brilliant in that I can pass a needle through them (no wood backing or other material), and they're light enough (no extra framing) to confidently hang from minimally intrusive hardware.
The results of putting up ProPanels are immediately noticeable without pulling out any fancy test equipment. Cancellation of slap and echo, and tightening of midrange frequencies, with less resonance and ringing, are the indisputable highlights. Even just walking into a room that's gone from no sound treatment to a few mounted ProPanels can be a difference that your ears can detect right away. In one of the rooms I treated, I had a large, deep window, and I had grown accustomed to the "boominess" on that side of the room. Initially, I didn't consider ProPanels in this space since I was wary of using them as bass traps. But eventually, I rested a couple of the panels inside the window opening and was blown away by the result. The low-frequency resonance was reduced significantly, and that room was transformed into a space I could trust working in. That's the power of sound treatment, and if you can do it simply and effectively, you're way ahead of the curve.
I've collaborated with lots of musicians over the years who've never treated their rooms (obviously, I was in this group too at one time), and it's painful to think of how much frustration inevitably follows. If the room in which you're recording or mixing has uncontrolled peaks and valleys in frequency-response and reverb-time, then you simply won't capture an accurate image with your mics, and your speakers won't convey an accurate soundstage. Therefore, any work you do in that room may not "translate" well to someone else's room, space, or even crappy earbuds. When you consider the budget that the typical musician, recordist, or studio spends on gear and software, the cost of basic room treatment can be laughably low in comparison - especially when you consider the vast improvements the treatment can make to the recordings and mixes, let alone the performances too.
ELiTE ProPanels also comply with all LEED (Leadership in Energy and Environmental Design) qualifications, meaning they're environmentally friendly (using significant recycled content), they're manufactured using fewer pollutants (formaldehyde and phenol are totally eliminated from the fabrication process), and they release lower amounts of VOCs (volatile organic compounds) into the air. It's always great to see companies paying attention to the environment and our health.
While these panels alone won't treat every acoustic problem plaguing a room (but no worries - Auralex can sell you pretty much any acoustical treatment you need, including materials for ground-up construction), ELiTE ProPanels exhibit an exceptional blend of effectiveness, aesthetics, dead-simple installation, durability, and affordability. ProPanels can be purchased as individual panels or in various room kits. Auralex even offers a few different levels of personalized room analysis to customize treatment recommendations for your specific room. You can check out all these options on the company website.