I don't consider the Impreza a premium car in the traditional sense. Nor the WRX or the Saab 9-2X for that matter.
They are darnright crampy inside IMO, but that's not what strikes it off the premium list for me. Sure, it's built well... but not built out of premium materials. They don't radiate quality - the interior materials aren't up to snuff, the controls don't switch with smoothness, the features are nothing remarkable or ground-breaking. The audio unit isn't spectacular as far as I know. There's few premium features... no HIDs (save for STi, or does that not even have them?), no NAVI.
What you have is something functional and durable. Sure, that's worth something, but it's not 'premium' to me. At least not in the Impreza range. The Legacy I'll let pass and agree has some 'premium mid-size' status to it.
What is there? Performance. It's a premium on performance. The handling, the stability, the AWD in winter, and the AWD to fire you off the mark in the WRX and STi.
And while I think the NEW Subarus have gotten further into the premium side of things, particularly Legacy and B9 Tribeca, the Imprezas aren't yet there for me.
And while the VWs I believe are further there, they need to combine that with electrical quality that matches the perceived quality. But I believe that is easier to do than the reverse engineering.
Sounds silly but I always equate luxury to a wooden jewelry box. You could get one that's large and holds lots, perfectly cut by machine, hinged and opens fine, and looks otherwise okay and is very practical for the use of storing jewelry. It's practical. By all accounts it serves it's intended purpose well with little fuss. But what makes something premium is the extra care - it IS the hand crafting, the polished finish, the quality of construction, the special metallic hinges or closing mechanism, the quality of padding on the interior to cushion the jewelry... the exclusiveness and first and foremost attention to detail. Okay, that may be going a tad overboard, but that's what does it for me, and how I distinguish.
For me, the interior materials are VERY important when evaluating a car and giving it premium status. I could make something out of Rubbermaid and give it AWD, but that doesn't make it good. Actually, nowadays many cars are built so solid and with such attention to design detail that I believe it IS getting harder to justify paying more for luxury goods and cars... that's why the AWD, exterior and interior colours and selection / personalization, and ever increasing horsepower powerplants are coming back.
The new Civic is a good example. It's a darned good car! Looks great to me inside and out. Interior is ground-breaking and as far as I'm concerned makes the Subaru look like an 80's child. Materials are perfectly fine. Not 'premium', but something had better rope me in via it's power/quietness/interior quality/ride/handling/whatever-else for me to really want anything more. What people buy the Accord for the Civic can do nearly just as well now, so how does someone decide the price jump to an Accord is justified?
Anyhow, getting off track, but 'premium' is hard to quantify and means something different to everyone I think.