Hi, I totally agree with most comments here about the richness of VSL, and I would like to share my impression with VSL here too.
I started to know VSL when I was looking for a way to upgrade my Sibelius and to make it sound better. My first purchase, Special Edition 1, did the job well and helped my composition workflow even though I didn't feel much impressed with the sound quality. (I thought it was too dry, but I didn't know the reason at the moment.) I expanded it to SE1+ to get more articulations and tried the demo MIRx before finding out that it helped improve the sound a lot. I would say that Special Editions and MIRx are a perfect combination for notation software (plus VI Pro if you need access to polyphonic legato feature).
However, when it comes to DAW sequencing, I found it difficult to achieve the realism, especially for solo instrument phrases, with only SE and MIRx. The articulations were just not enough for me to make a phrase sound musically coherent. At times, I was caught in a dilemma whether I should upgrade my VSL, or just go for other libraries that sound good out-of-the-box.
I read lots of forums and did some research on VSL product lines. I realised that the philosophy behind VSL is different from other. They recorded the samples dry, therefore the most important parts to achieve great sounding are their software: VI Pro, MIR Pro, and Vienna Suite. The result of VSL approach is greater flexibility and more precise control over the sound of the instruments, but in an expense of a higher learning curve and being more complicated to deal with. I ended up getting the Solo Strings I and was amazed at its huge amount of articulations and result I could get with it.
Since then, I have kept visiting the VSL website every month to see which instrument was on discount and started to build up my VSL palette patiently. To anyone who is new to VSL, I would recommend starting with the combination of SE1, VI Pro and MIRx. Then, considering upgrading your frequently used solo instruments to the full library for more details and better realism. Software-wise, the best upgrading path, in my opinion, is MIRx>MIR PRO (24) with one RoomPack, before getting the Vienna Suite. (I skipped VEP because it has nothing to do with the sound but it becomes very handy when you have a huge template and have to set up a master-slave network.)
Although VSL samples and software have been the main part of my templates, I still love experimenting with other company's libraries and use them, either on its own or layering them with VSL, every now and then. Sometimes they just sound right in certain situations. I believe that there is no best sample library in the market, but the consistency, flexibility and the wide range of articulations that VSL offer just allows its users to achieve a very close result to recording real orchestral musicians.
PP