Not everyone has the luxury of running a Cisco UCS server at home. Even if you do, it's a little bit heavy to drag the UCS around. It would be convenient to have the UC lab built on your laptop.
I myself am using VMware Workstation 9.0.2 on a ThinkPad T430 with 16G RAM/1TB HDD. Some of the laptops (such as ThinkPad W-series) allow you go for 32G RAM, which is really helpful if you need to run multiple boxes (such as UCM, UCCX, UCXN, CUPS, CER, AD) at the same time.
Personally, I prefer creating the VM spec myself instead of importing the OVA file from Cisco. Some of the spec in OVA doesn't make sense in a lab environment. (For example, what good would it do to have 2 vCPU in the VM while you're running it on a laptop?)
For the VM hard drive, I always use thin provisioning and use one single file.
For VM network, I'd prefer "host-only network" unless you have other external components need to talk to the UC lab.
Depending on your UC version, you might run into strange problems that the UC box can't ping anywhere in "host-only network" (not even the VMs in the same network). For example, I ran into this problem with UCCX 8.5.1 while UCM 8.6.2 was fine. The solution is to upgrade VMTools on the UC box.
In later versions, NTP and DNS become mandatory. You may set up those on your Windows 7 desktop (your host OS), so you don't need a dedicated Windows server to do that. For NTP, it's built in Win7. Just follow the procedure on http://htluo.blogspot.com/2009/02/ntp-network-time-protocol.html. For DNS, you may google for some freeware or shareware.
In a "host-only network", you have the option to have a host adapter connects to the network. So you may connect to the UC boxes from your host OS (e.g. run CIPC from your Win7 desktop). By default, the "host-only network" is in the 192.168.130.0 network (or a random class-C in the 192.168 range). You may change it. You may also change the host adapter (default is VMnet1) IP address. If the change didn't seem to take effect, please check the 'Advanced' button in the TCP/IP bindings. You might have multiple IP addresses bound to the VMnet1 adapter.