Hello, VSF (Virtual Switching Framework) is recent (for sure it can be considered almost new if compared to the best known HPE IRF) but not exactly new (first informations about VSF appeared during late 2015 here at Atmosphere 2015 for ANZ region...but searching for "VSF" and "5400R" terms, either on this HPE Community or on Aruba AirHeads, you will be able to figure out that some other post were written, curiously more on HPE Community than on Aruba AirHeads).
Probably one of the very first HPE Community post (on Networking category) in which the term VSF was named is this one...then VSF was discussed again.
About the fact you consider it potentially buggy (because too new)...personally I don't know (I can't judge): I only know that VSF was introduced since the first KB.16.01 software branch release (January 2016) and, after that, at least five or six software version updates (16.0x.nnnn) were released respectively for both KB.16.01 branch and for the new KB.16.02 branch (KB.16.02 branch started on August 2016)...so you should be able to figure out how much stable it is - now - by searching and counting about known VSF-related bugs one various Release Notes, bugs that were - obviously - already fixed (no one will be able to tell you about new bugs simply because new bugs are - as of now - unknown). Clearly that's a totally empirical method...nothing to be taken too seriously.
For sure there are other VSF related bugs which are currently being fixed/diagnosed/evaluated...will be interesting to know how many VSF deployments are running out there (to infer if the total number of bugs is high or low with respect to the total number of VSF deployments made in less than a year)...but, I think, that number will be difficult to gather only by counting VSF related users' posts here and there.
OTOH I suggest you to read the ArubaOS VSF Configuration Guide to understand which type of "redundancy" and "load balancing" you will be able to obtain by implementing a VSF solution with two Aruba 5406R zl2 (or with two Aruba 5412R zl2) units.
For more details the Chapter 20 (it's about fifty pages long) of the HPE ArubaOS-Switch Management and Configuration Guide K/KA/KB.16.02 (pick up the latest published in September for 16.02 branch to read up-to-date informations) is entirely dedicated to VSF.
If you read those documents you will be able to find the answers for all your questions (and other questions can be approximately answered reading some other VSF related posts written until these days).
Another HPE alternative way to implement Virtual Switching would be the one that is not relaying on VSF (VSF is - actually - specifically Aruba 5400R zl2 centric) but is instead based on a IRF Stack solution which is a technology well developed and supported on various Comware based HPE Switches (IRF would move you from ArubaOS-Switch - which is the rebranded/developed/enhanced version of the legacy well known HP ProCurve's ProVision operating system - to land on the Comware territory)...but that's up to your deployment requirements.
Hope this help.