The idea behind hal Bar is great and undoubtedly many are going to find this software incredibly useful including myself.
Now for some suggestions. Im sure some have already been suggested. And there may be some things I mention here that are aready implemented?
1. A function to allow the user to shift the whole spectrum either left or right. This would save time when you want to get your spectrum roughly in the same ballpark when comparing/matching with a reference filter.
2. Some Character addition to the EQ is needed if Hal bar is to remain competitive. I find the EQ to be good but some flavour as an option should be added. Covultion/sampled EQ would be a perfect choice. I dont think you would have to sample a hardware unit to quite the extent the Hydratone people do but you could do some basic flavours with some Hi end gear to give Hal Bar character if the user requires. This would be great for Hal bar I have no doubt of that. voxengo has many of these features and they are very very good.
3. A function that allows faster switching spectrums. Im working on a mix I like what I have and save the Spectrum and start working on another one etc etc. I want to be able to switch between spectrums fast and in real time. Firium has this function and allows the user to morph different spectrums. Hal Bar doesnt need to Morph as theres no need for that during mastering. Being able to swicth easily between spectrums would be very useful. Around ten readily available woudl be great.
4. Im not sure about this one but Hal Bar doesnt seem to allow full free hand drawing of curves? I think this is an essential feature.
5. A standalone VST halbar Spectrum display. I realise this may not be music to your ears because why would anyone need to buy Hal Bar if they can simply use a spectrum analyser and a decent Phase/paramteric EQ to achieve the same results. Well it should be sold with the full version of hal bar. Lets face it one can download a free Spectrum analyser from a certain site and do just as Im saying but your display is the best one out there. Simple and clean.
6 No. Vst implementation. I totally agree with your policy regarding this. However it does mean you are cutting out a lot of potential buyers so at least adding the spectrum analysis only version would sort of pacify those that want VST functionality. I woudl like it.
7. While your not actively promoting EQ match (and rightly so) I still think the feature should be there with a big red button

8. Match Loudness. having a bit of difficulty with this one. I have some thoughts but will wait before I post them. Exactly what is going on here? Is there something going on in the background or is this simply changing gain?
Thats all for now. I will probably add to this as I use Hal Bar. It seems Im best to write these things as Im using it. Im sure theres more I wanted to say I just cant remember et the moment.
Hal Bar is a great tool and already I have remastered a couple of tracks which Im very happy with. I would have been even more happier if I was able to add character to the mix (hence Convultion). I then wouldnt need to bring teh track in to my DAW to do further work. I generally get my RMS in teh right ballpark when I mixdown and would rather finish the process entirely within Hal Bar. Your site seems to push the...... use Hal Bar and then import to a DAW when in reality this is not always nescessary if the engineer/producer is slapping compression/limiting on during the mixdown. All Im saying here is that totally promoting the use of an L2 is maybe not the best suggestion and could actually be destructiove to the mix. personally I try and stay clear of L2/L3. If I do use one it would be an L1.