Here's my opinions on aluminum cases in general. Disclaimer - I'm only going to mention cases I've owned or worked with.
Lian Li "6" series: Decent design and nice metal thickness. Used to be way too expensive, but now there's some nice ones hovering around $100 (had my eye on a 7Plus with front/rear 120mm fans for around $120). Would like to see a "refresh" in these more budget units, such as using finger guards for better airflow and using rubber grommets for HDD mounts, plus false fronts for optical drives.
Aspire "alien" series: These Chenming cases have been popular with the aftermarket crowd for years under different brands and with slightly differing designs. Mine had the sideways HDD mounts. The case has great airflow but the ones I've used all were noisy with included fans. Reasonably sturdy for an aluminum case. The aluminum versions of these hover just over $100. Good for those wanting a more pimped out look, but don't want to pay double for a Thermaltake with the same chassis.
Antec LAN Boy: I actually had the original Chenming version. Aspire had their version. This was probably one of the lightest aluminum cases I've ever owned, because the metal was the most thin. The bottom of mine started to develope a permanent bend just from the weight of the components. The chassis is actually rather stiff when both side panels are bolted firmly on. Great airflow, few HDD bays, inexpensive at $40-60 depending on branding/features. Good choice for a minimal system for LAN parties (minimal meaning single HDD, single optical, no copper HSF).
Antec Super LAN Boy: I really like this case design, except for the "waffle" front grill which is easily solved with a finger guard. Oh yeah, don't really like doors over drive bays, but it does hide the mismatching optical drives.

I don't know why people think this case is flimsy because the only aluminum cases I've used (note: only comparing to cases in this list) that were more sturdy have been the Lian Li, Aspire "alien" and AOpen, and all are more expensive. The SLB case can be had for under $50 with the constant rebate deals going on for the past year - a steal at that price. It's lightweight, comes with carrying straps, has decent cooling and is relatively quiet. Nothing cheaper can match the cooling or quietness - comparing stock, unmodified.
AOpen A600B: This is a beautiful but understated case. It has a smallish side window, 3 color rear 120mm fan and has 6 internal drive bays. The power button is lit up and cycles through various colors. Lighting isn't too bright, so it doens't actually draw too much attention to itself. The finish is a nice glossy one but does take some work to keep it nice (just like any other glossy finish), even came with a polishing chamois-like cloth. Comes with a 3 position speed controller that can control rear fan plus a second one. This one is kinda big, so better for the stationary system and not a LAN party box. Ventilation is good, but rear fan could use a finger guard instead of punched out grill. Comes with a 300w PSU made by Fortron (judging from model#) and runs about $130. A real suprise from AOpen. They now need to cut a few bucks off, use a finger guard in rear and sell it w/o PSU.
A+GPB mATX: The chassis design is
similar to this case. These seem to be discontinued and indeed A+GPB no longer exists, but morphed into Athena Power. The power supply is kinda an SFX form factor, but a few companies make really nice ones that bolt right in, TTGI and Enermax. We're talking high amperage quality PSU that fit. I still own two of these cases. The aluminum is reasonably thick and the chassis is rigid. Rear has two 60x15mm or so fans in a plastic holder. The punched out grill can easily be snipped off with dykes, similar to the ones on the original Shuttle SV24 (concentric, just four snips and it falls out). Side panel has no holes in it at all. Front face is plastic with a plexiglass cover. The "bottom" of the front (if stood up like a tower) looks like the vents in the Antec P160 series, complete with blue LEDs. I had a rockin' gaming machine built into one of these for a while with a Chaintech Nforce2 Ultra 400 mATX board, mobile Barton CPU overclocked with wire trick, 6800GT video and Enermax PSU. Only drawback of chassis is that it is so small that most optical drives interfere with larger HSFs. My temporary solution was an external USB optical drive.
Skyhawk cases: I have gone through a number of the older style chassis - the ones with only a 60mm exhaust fan option and not too many internal drive bays. They were pretty flimsy. Not just the thinness of the aluminum, but seems like they used a lower grade alloy because the LAN Boy cases seem as thin, but also seemed more rigid. My first one was years ago with an "X" side window, using it with a Tualatin CPU and cost about $70 shipped from SVC.com back when most aluminum cases were $200 and few cases came with side windows. My most recent one was purchased from Dumpinggoods.com for about $25 shipped (yes, shipped) and I got it just as a spare chassis. They are, um, okay for the price. Horrible ventilation with small fans and, "WTF, no holes in the face?!?!" Front ports go out the rear and just plug into regular ports instead of motherboard headers. These cases are cheaper than cheap. I would only recommend them for people who have a cooler running system and need a really cheap, nice looking case (BTW, they are all nicer looking than a "beige box" without screaming "14yr old gamer"). Otherwise, better options are out there.
Skyhawk "server" chassis: I just ordered one yesterday from Dealsonic, will see how it goes. Initial observations from talk around here and pics are that it makes for a budget modding platform. Seems to have smart design aspects and be of reasonable quality. [MAD DOCTOR]Looking forward to cutting into it.[/MAD DOCTOR]
Observations on other cases that I haven't seen in person:
Antec P160: Looks like a smart design emphasizing quiet and airflow.
Lian Li V1000: "Different," dunno about all that mesh. I'm from the thought that airflow should be directed, not just allowed to dissipate.
Kingwin KT424: I've been looking for an excuse to get one because it just looks sharp and has nice design features, but alas I keep finding other choices.
Aspire X-Qpack: I was one of the first to mention the case here. If it had just )( that much more depth so that standard PSU and longer optical drives could fit...
Thermaltake: Don't like their design.