Hi Bradley,Broadly speaking yes, but there are some things to bear in mind 
First question first, yes you can run myriad v3.0 and v3.5 on different workstations looking at the same data files without any major issues.
You can even install 3.0 and 3.5 on the same computer,but obviously you can actually only RUN one at a time - you need to quit from 3.0 before running 3.5 and vice versa as you should only run one copy of Myriad at a time or things get very messy!
The system is actually designed that way becuase we wanted to give the most flexibility to users when it comes to migrating. We also need to be able to provide tech support for both versions here in the office so we have to have both installed on our desktop pc's here as well!
There shouldn't be any real problems with going back to 3.0 if you decide to.
The only major things to watch out for are:
1) The Audiowall in 3.5 contains extra settings that 3.0 doesn't support - i.e. Execute Commands, Content Type and Genre coding. If you edit a 3.5 cart that has these set using Mv3.0 those settings will be lost.
2) The Macro language in 3.5 has been expanded enormously, and any of the new macros that you add to a command won't work under 3.0
3) The Database is stored slightly differently in 3.5 than 3.0 to allow for features like InstantTrack. Ideally you should create a new Station Database to use for 3.5 but this isn't essential (unless you previously ran the Alpha version in which case you have to!)
4) If you are using AutoTrack you should download the latest v3 release as it contains support for the upgraded Database format and also has special support so it doesn't erase the new features on the Carts that it doesn't understand.
(Later this year we are hoping to release a v3.5 of AutoTrack that has full support for those features)
Hope that helps, any questions then obviously please let me know
Cheers
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Peter Jarrett, Technical Director
P Squared Ltd.Bill Bailey: "No win, no fee, no basis in reality. Just a room above a minicab office in Acton and a steady stream of greedy simpletons whose delusion is only matched by their clumsiness"