I don't normally advertise what's [hopefully] already known, but, 4.5 is a big step forward, and not just in the name change :)

http://blogs.technet.com/smsandmom/archive/2007/11/12/microsoft-application-virtualization-4-5-is-open-for-public-beta.aspx 

Yes, When v4.5 is released we will support the client upgrade from 4.2 and respect the settings.

[update 8th Nov]

Ok, so what about your sequenced applications, will they work? Yes, we expect applications sequenced in 4.2 to work just fine on the new 4.5 client, however, there will always be some edge cases and in those circumstances it might require the application to be unpacked to a 4.5 sequencer, and then saved again (not re-sequenced).

As with previous updates, it is recommended practice to upgrade all the clients first, then the servers. 4.2 clients will not connect to 4.5 servers, 4.5 clients will connect to 4.2 servers.

An application would also need to be re-sequenced (or upgraded) if you wanted to use some of the new features of 4.5, for example, multi-language support, dynamic suite composition, etc.

The recommended practice is to choose a virtual drive assignment and stick to it; commonly, this is drive Q: - so what happens if you want to change to something else, for example, V:

If all applications were equal and followed recommended practice, then simply changing the environment variable %SFT_MNT% on the client would enable you to change the virtual drive at will and no applications would need to be re-sequenced; however, not all applications are equal and this can cause some issues.

Some applications hard code the installation drive in the registry or configuration (INI) files - This means you have several options:-

1. Re-sequence the application to the new virtual drive letter.
2. Sequence the application to the C: drive (be aware of the performance impact of doing this)
3. Manually edit the applications registry entries or configuration files

As with all applications, if you decide to have a different client virtual drive compared to the sequencer then testing will be paramount.

No. Not yet.

AIS (Application Inventory Service, part of the Microsoft Desktop Optimisation pack (MDOP)), delves deeper into a machine than most inventory software services, besides the add/remove MSI components, it also checks the registry etc. However, SoftGrid applications are not registered in the add/remove or in the registry, in fact, pretty much no-where; therefore no software asset service will find SoftGrid applications.

This will change going forward, for example, customers who adopt the MSI Utility and/or ESD (Electronic Software Distribution) technologies will register SoftGrid in the Add/Remove MSI components and this will in turn allow asset inventory services to detect SoftGrid applications deployed in this way (but not streamed applications).

If an Asset Inventory service was SoftGrid aware, then it could call the SoftGrid client and ask what applications were installed.

The sequencer can be a real machine or a virtual machine; commonly, virtual machines are used for the following reasons:-

• They can be reverted back to a known consistent state via undo or simple file copy routines.
• They can be manipulated via scripts and have their content changed remotely
• You can run multiple simultaneous copies on the same machine, or on dispersed host machines.
• They can be created and destroyed with a very fast turn-around

There are times however when a real computer is required; for example:-

• A specific piece of hardware is required, for example a fax card, USB device, or graphics sub-system.

If you have concerns over the performance of a virtual machine, see my items on performance, specifically on processor count.