Powershell ISE is quite a good terminal emulator (even tho it wasn't intended as one), it's also extensible via addons and there are quite a few nifty ones like git integration and the likes.
This is the ISE in a default configuration https://imgur.com/xz9Kfpt
On the left just an open terminal, in the middle a script which can be edited and executed at any time with F5, and on the right all the powershell commands which could be either immediately executed or inserted into your script with ease.
Unless you need tab browsing that much, which you can get via addons, the ISE is one of the best "terminals" out there imho.
On my i5-2400 with 8 GB of RAM and a 7200 RPM hard drive, it takes six seconds to start the first time and four seconds to start subsequent times.
On my i5-3550 with 16 GB of RAM and an SSD it takes a couple seconds to start the first time and less than a second for subsequent times.
Both machines are running Windows 10.
Right now, the machine with the spinning rust is loading a bunch of files with an I/O priority of "background" because it just got booted into Windows; that might slow it down a bit because of the seek times and I don't know if Windows is willing to starve background I/O for seconds at a time to speed up interactive requests (I doubt it).
Update: once all the background preloading is done, PowerShell restarts in three seconds on the spinning-rust machine.
Long story short, I think getting an SSD will be the thing that makes PowerShell start acceptably fast.
Speed was an issue on Windows 7 (PSv2), but they sped it up considerably in Windows 8 (PSv4, I think). Maybe installing the current PowerShell version helps; I doubt it's inherent in the OS.
I'm on Windows 10 and I agree it has improved a lot since Win7, but it's still not pleasant. I'm rocking a 7200rpm spinning disk, so as suggested by adiabatty, getting an SSD might help.
Depending what you open, powershell.exe should open as fast as cmd.exe pretty much, the ISE can take a few seconds to load based on the addons you have and how many PS cmdlets you have registered on your system.
As people have mentioned the biggest factor here is probably your hard drive since you are loading maybe couple of 100's of small files when you load the ISE.